Articles

20 Obstacles to Scalability:
Watch out for these pitfalls that can prevent Web application scaling.

Web applications can grow in fits and starts. Customer numbers can increase rapidly, and application usage patterns can vary seasonally. This unpredictability necessitates an application that is scalable. What is the best way of achieving scalability?

A Call to Arms:
Long anticipated, the arrival of radically restructured database architectures is now finally at hand.

We live in a time of extreme change, much of it precipitated by an avalanche of information that otherwise threatens to swallow us whole. Under the mounting onslaught, our traditional relational database constructs—always cumbersome at best—are now clearly at risk of collapsing altogether. In fact, rarely do you find a DBMS anymore that doesn’t make provisions for online analytic processing. Decision trees, Bayes nets, clustering, and time-series analysis have also become part of the standard package, with allowances for additional algorithms yet to come. Also, text, temporal, and spatial data access methods have been added—along with associated probabilistic logic, since a growing number of applications call for approximated results.

A Decade of OS Access-control Extensibility:
Open source security foundations for mobile and embedded devices

To discuss operating system security is to marvel at the diversity of deployed access-control models: Unix and Windows NT multiuser security; Type Enforcement in SELinux; anti-malware products; app sandboxing in Apple OS X, Apple iOS, and Google Android; and application-facing systems such as Capsicum in FreeBSD. This diversity is the result of a stunning transition from the narrow 1990s Unix and NT status quo to ’security localization’ - the adaptation of operating-system security models to site-local or product-specific requirements.

A File System All Its Own:
Flash memory has come a long way. Now it’s time for software to catch up.

In the past five years, flash memory has progressed from a promising accelerator, whose place in the data center was still uncertain, to an established enterprise component for storing performance-critical data. It’s rise to prominence followed its proliferation in the consumer world and the volume economics that followed (see figure 1). With SSDs (solid-state devices), flash arrived in a form optimized for compatibility - just replace a hard drive with an SSD for radically better performance. But the properties of the NAND flash memory used by SSDs differ significantly from those of the magnetic media in the hard drives they often displace.

A Guided Tour through Data-center Networking:
A good user experience depends on predictable performance within the data-center network.

The magic of the cloud is that it is always on and always available from anywhere. Users have come to expect that services are there when they need them. A data center (or warehouse-scale computer) is the nexus from which all the services flow. It is often housed in a nondescript warehouse-sized building bearing no indication of what lies inside. Amidst the whirring fans and refrigerator-sized computer racks is a tapestry of electrical cables and fiber optics weaving everything together -- the data-center network.

A High-Performance Team:
From design to production, performance should be part of the process.

You work in the product development group of a software company, where the product is often compared with the competition on performance grounds. Performance is an important part of your business; but so is adding new functionality, fixing bugs, and working on new projects. So how do you lead your team to develop high-performance software, as well as doing everything else? And how do you keep that performance high throughout cycles of maintenance and enhancement?

A Hitchhiker’s Guide to the Blockchain Universe:
Blockchain remains a mystery, despite its growing acceptance.

It is difficult these days to avoid hearing about blockchain. Despite the significant potential of blockchain, it is also difficult to find a consistent description of what it really is. This article looks at the basics of blockchain: the individual components, how those components fit together, and what changes might be made to solve some of the problems with blockchain technology.

A New Objective-C Runtime: from Research to Production:
Backward compatibility always trumps new features.

The path from the research prototype (Étoilé runtime) to the shipping version (GNUstep runtime) involved a complete rewrite and redesign. This isn’t necessarily a bad thing: part of the point of building a prototype is to learn what makes sense and what doesn’t, and to investigate what is feasible in a world where you control the entire system, but not necessarily in production.

A New Software Engineering:
What happened to the promise of rigorous, disciplined, professional practices for software development?

What happened to software engineering? What happened to the promise of rigorous, disciplined, professional practices for software development, like those observed in other engineering disciplines? What has been adopted under the rubric of "software engineering" is a set of practices largely adapted from other engineering disciplines: project management, design and blueprinting, process control, and so forth. The basic analogy was to treat software as a manufactured product, with all the real "engineering" going on upstream of that - in requirements analysis, design, modeling, etc.

A Passage to India:
Pitfalls that the outsourcing vendor forgot to mention

Most American IT employees take a dim view of offshore outsourcing. It’s considered unpatriotic and it drains valuable intellectual capital and jobs from the United States to destinations such as India or China. Online discussion forums on sites such as isyourjobgoingoffshore.com are headlined with titles such as “How will you cope?” and “Is your career in danger?” A cover story in BusinessWeek magazine a couple of years ago summed up the angst most people suffer when faced with offshoring: “Is your job next?”

A Pioneer’s Flash of Insight:
Jim Gray’s vision of flash-based storage anchors this issue’s theme.

In the May/June issue of Queue, Eric Allman wrote a tribute to Jim Gray, mentioning that Queue would be running some of Jim’s best works in the months to come. I’m embarrassed to confess that when this idea was first discussed, I assumed these papers would consist largely of Jim’s seminal work on databases showing only that I (unlike everyone else on the Queue editorial board) never knew Jim. In an attempt to learn more about both his work and Jim himself, I attended the tribute held for him at UC Berkeley in May.

A Plea to Software Vendors from Sysadmins - 10 Do’s and Don’ts:
What can software vendors do to make the lives of sysadmins a little easier?

A friend of mine is a grease monkey: the kind of auto enthusiast who rebuilds engines for fun on a Saturday night. He explained to me that certain brands of automobiles were designed in ways to make the mechanic’s job easier. Others, however, were designed as if the company had a pact with the aspirin industry to make sure there are plenty of mechanics with headaches. He said those car companies hate mechanics. I understood completely because, as a system administrator, I can tell when software vendors hate me. It shows in their products.

A Primer on Provenance:
Better understanding of data requires tracking its history and context.

Assessing the quality or validity of a piece of data is not usually done in isolation. You typically examine the context in which the data appears and try to determine its original sources or review the process through which it was created. This is not so straightforward when dealing with digital data, however: the result of a computation might have been derived from numerous sources and by applying complex successive transformations, possibly over long periods of time.

A Purpose-built Global Network: Google’s Move to SDN:
A discussion with Amin Vahdat, David Clark, and Jennifer Rexford

Everything about Google is at scale, of course -- a market cap of legendary proportions, an unrivaled talent pool, enough intellectual property to keep armies of attorneys in Guccis for life, and, oh yeah, a private WAN (wide area network) bigger than you can possibly imagine that also happens to be growing substantially faster than the Internet as a whole.

A Requirements Primer:
A short primer that provides background on four of the most important compliance challenges that organizations face today.

Many software engineers and architects are exposed to compliance through the growing number of rules, regulations, and standards with which their employers must comply. Some of these requirements, such as HIPAA, focus primarily on one industry, whereas others, such as SOX, span many industries. Some apply to only one country, while others cross national boundaries.

A Threat Analysis of RFID Passports:
Do RFID passports make us vulnerable to identity theft?

It’s a beautiful day when your plane touches down at the airport. After a long vacation, you feel rejuvenated, refreshed, and relaxed. When you get home, everything is how you left it. Everything, that is, but a pile of envelopes on the floor that jammed the door as you tried to swing it open. You notice a blinking light on your answering machine and realize you’ve missed dozens of messages. As you click on the machine and pick up the envelopes, you find that most of the messages and letters are from debt collectors. Most of the envelopes are stamped "urgent," and as you sift through the pile you can hear the messages from angry creditors demanding that you call them immediately.

A Time and a Place for Standards:
History shows how abuses of the standards process have impeded progress.

Over the next decade, we will encounter at least three major opportunities where success will hinge largely on our ability to define appropriate standards. That’s because intelligently crafted standards that surface at just the right time can do much to nurture nascent industries and encourage product development simply by creating a trusted and reliable basis for interoperability. From where I stand, the three specific areas I see as particularly promising are: (1) all telecommunications and computing capabilities that work together to facilitate collaborative work; (2) hybrid computing/home entertainment products providing for the online distribution of audio and/or video content; and (3) wireless sensor and network platforms (the sort that some hope the 802.15.4 and ZigBee Alliance standards will ultimately enable).

A Tour through the Visualization Zoo:
A survey of powerful visualization techniques, from the obvious to the obscure

Thanks to advances in sensing, networking, and data management, our society is producing digital information at an astonishing rate. According to one estimate, in 2010 alone we will generate 1,200 exabytes -- 60 million times the content of the Library of Congress. Within this deluge of data lies a wealth of valuable information on how we conduct our businesses, governments, and personal lives. To put the information to good use, we must find ways to explore, relate, and communicate the data meaningfully.

A Tribute to Jim Gray

Computer science attracts many very smart people, but a few stand out above the others, somehow blessed with a kind of creativity that most of us are denied. Names such as Alan Turing, Edsger Dijkstra, and John Backus come to mind. Jim Gray is another.

A co-Relational Model of Data for Large Shared Data Banks:
Contrary to popular belief, SQL and noSQL are really just two sides of the same coin.

Fueled by their promise to solve the problem of distilling valuable information and business insight from big data in a scalable and programmer-friendly way, noSQL databases have been one of the hottest topics in our field recently. With a plethora of open source and commercial offerings and a surrounding cacophony of technical terms, however, it is hard for businesses and practitioners to see the forest for the trees.

AI Gets a Brain:
New technology allows software to tap real human intelligence.

In the 50 years since John McCarthy coined the term artificial intelligence, much progress has been made toward identifying, understanding, and automating many classes of symbolic and computational problems that were once the exclusive domain of human intelligence. Much work remains in the field because humans still significantly outperform the most powerful computers at completing such simple tasks as identifying objects in photographs - something children can do even before they learn to speak.

AI in Computer Games:
Smarter games are making for a better user experience. What does the future hold?

If you’ve been following the game development scene, you’ve probably heard many remarks such as: "The main role of graphics in computer games will soon be over; artificial intelligence is the next big thing!" Although you should hardly buy into such statements, there is some truth in them. The quality of AI (artificial intelligence) is a high-ranking feature for game fans in making their purchase decisions and an area with incredible potential to increase players’ immersion and fun.

API: Design Matters:
Why changing APIs might become a criminal offense.

After more than 25 years as a software engineer, I still find myself underestimating the time it will take to complete a particular programming task. Sometimes, the resulting schedule slip is caused by my own shortcomings: as I dig into a problem, I simply discover that it is a lot harder than I initially thought, so the problem takes longer to solve—such is life as a programmer. Just as often I know exactly what I want to achieve and how to achieve it, but it still takes far longer than anticipated. When that happens, it is usually because I am struggling with an API that seems to do its level best to throw rocks in my path and make my life difficult.

ASPs: The Integration Challenge:
The promise of software as a service is becoming a reality with many ASPs.

Organizations using ASPs and third-party vendors that provide value-added products to ASPs need to integrate with them. ASPs enable this integration by providing Web service-based APIs. There are significant differences between integrating with ASPs over the Internet and integrating with a local application. When integrating with ASPs, users have to consider a number of issues, including latency, unavailability, upgrades, performance, load limiting, and lack of transaction support.

Above the Line, Below the Line:
The resilience of Internet-facing systems relies on what is below the line of representation.

Knowledge and understanding of below-the-line structure and function are continuously in flux. Near-constant effort is required to calibrate and refresh the understanding of the workings, dependencies, limitations, and capabilities of what is present there. In this dynamic situation no individual or group can ever know the system state. Instead, individuals and groups must be content with partial, fragmented mental models that require more or less constant updating and adjustment if they are to be useful.

Abstracting the Geniuses Away from Failure Testing:
Ordinary users need tools that automate the selection of custom-tailored faults to inject.

This article presents a call to arms for the distributed systems research community to improve the state of the art in fault tolerance testing. Ordinary users need tools that automate the selection of custom-tailored faults to inject. We conjecture that the process by which superusers select experiments can be effectively modeled in software. The article describes a prototype validating this conjecture, presents early results from the lab and the field, and identifies new research directions that can make this vision a reality.

Abstraction in Hardware System Design:
Applying lessons from software languages to hardware languages using Bluespec SystemVerilog

The history of software engineering is one of continuing development of abstraction mechanisms designed to tackle ever-increasing complexity. Hardware design, however, is not as current. For example, the two most commonly used HDLs date back to the 1980s. Updates to the standards lag behind modern programming languages in structural abstractions such as types, encapsulation, and parameterization. Their behavioral semantics lag even further. They are specified in terms of event-driven simulators running on uniprocessor von Neumann machines.

Accountability in Algorithmic Decision-making:
A view from computational journalism

Every fiscal quarter automated writing algorithms churn out thousands of corporate earnings articles for the AP (Associated Press) based on little more than structured data. Companies such as Automated Insights, which produces the articles for AP, and Narrative Science can now write straight news articles in almost any domain that has clean and well-structured data: finance, sure, but also sports, weather, and education, among others. The articles aren’t cardboard either; they have variability, tone, and style, and in some cases readers even have difficulty distinguishing the machine-produced articles from human-written ones.

Achieving Digital Permanence:
The many challenges to maintaining stored information and ways to overcome them

Today’s Information Age is creating new uses for and new ways to steward the data that the world depends on. The world is moving away from familiar, physical artifacts to new means of representation that are closer to information in its essence. We need processes to ensure both the integrity and accessibility of knowledge in order to guarantee that history will be known and true.

Adopting DevOps Practices in Quality Assurance:
Merging the art and science of software development

Software life-cycle management was, for a very long time, a controlled exercise. The duration of product design, development, and support was predictable enough that companies and their employees scheduled their finances, vacations, surgeries, and mergers around product releases. When developers were busy, QA (quality assurance) had it easy. As the coding portion of a release cycle came to a close, QA took over while support ramped up. Then when the product released, the development staff exhaled, rested, and started the loop again while the support staff transitioned to busily supporting the new product.

Advances and Challenges in Log Analysis:
Logs contain a wealth of information for help in managing systems.

Computer-system logs provide a glimpse into the states of a running system. Instrumentation occasionally generates short messages that are collected in a system-specific log. The content and format of logs can vary widely from one system to another and even among components within a system. A printer driver might generate messages indicating that it had trouble communicating with the printer, while a Web server might record which pages were requested and when.

Agile and SEMAT - Perfect Partners:
Combining agile and SEMAT yields more advantages than either one alone

Today, as always, many different initiatives are under way to improve the ways in which software is developed. The most popular and prevalent of these is the agile movement. One of the newer kids on the block is the SEMAT (Software Engineering Method and Theory) initiative. As with any new initiative, people are struggling to see how it fits into the world and relates to all the other things going on. For example, does it improve or replace their current ways of working?

Algorithms Behind Modern Storage Systems:
Different uses for read-optimized B-trees and write-optimized LSM-trees

This article takes a closer look at two storage system design approaches used in a majority of modern databases (read-optimized B-trees and write-optimized LSM (log-structured merge)-trees) and describes their use cases and tradeoffs.

All Your Database Are Belong to Us:
In the big open world of the cloud, highly available distributed objects will rule.

In the database world, the raw physical data model is at the center of the universe, and queries freely assume intimate details of the data representation (indexes, statistics, metadata). This closed-world assumption and the resulting lack of abstraction have the pleasant effect of allowing the data to outlive the application. On the other hand, this makes it hard to evolve the underlying model independently from the queries over the model.

An Open Web Services Architecture:
The name of the game is web services.

The name of the game is web services-sophisticated network software designed to bring us what we need, when we need it, through any device we choose. We are getting closer to this ideal, as in recent years the client/server model has evolved into web-based computing, which is now evolving into the web services model. In this article, I will discuss Sun Microsystems’ take on web services, specifically Sun ONE: an open, standards-based web services framework. I’ll share with you Sun’s decision-making rationales regarding web services, and discuss directions we are moving in.

Anatomy of a Solid-state Drive:
While the ubiquitous SSD shares many features with the hard-disk drive, under the surface they are completely different.

Over the past several years, a new type of storage device has entered laptops and data centers, fundamentally changing expectations regarding the power, size, and performance dynamics of storage. The SSD (solid-state drive) is a technology that has been around for more than 30 years but remained too expensive for broad adoption.

Another Day, Another Bug:
We asked our readers which tools they use to squash bugs. Here’s what they said.

As part of this issue on programmer tools, we at Queue decided to conduct an informal Web poll on the topic of debugging. We asked you to tell us about the tools that you use and how you use them. We also collected stories about those hard-to-track-down bugs that sometimes make us think of taking up another profession.

Arm Your Applications for Bulletproof Deployment: A Conversation with Tom Spalthoff:
Companies can achieve a reliable desktop environment while reducing the time and cost spent preparing high-quality application packages.

The deployment of applications, updates, and patches is one of the most common - and risky - functions of any IT department. Deploying any application that isn’t properly configured for distribution can disrupt or crash critical applications and cost companies dearly in lost productivity and help-desk expenses - and companies do it every day. In fact, Gartner reports that even after 10 years of experience, most companies cannot automatically deploy software with a success rate of 90 percent or better.

Arrogance in Business Planning:
Technology business plans that assume no competition (ever)

In the Internet addressing and naming market there’s a lot of competition, margins are thin, and the premiums on good planning and good execution are nowhere higher. To survive, investors and entrepreneurs have to be bold. Some entrepreneurs, however, go beyond "bold" and enter the territory of "arrogant" by making the wild assumption that they will have no competitors if they create a new and profitable niche. So it is with those who would unilaterally supplant or redraw the existing Internet resource governance or allocation systems.

Attack Trends: 2004 and 2005:
Hacking has moved from a hobbyist pursuit with a goal of notoriety to a criminal pursuit with a goal of money.

Counterpane Internet Security Inc. monitors more than 450 networks in 35 countries, in every time zone. In 2004 we saw 523 billion network events, and our analysts investigated 648,000 security “tickets.” What follows is an overview of what’s happening on the Internet right now, and what we expect to happen in the coming months.

Automated QA Testing at EA: Driven by Events:
A discussion with Michael Donat, Jafar Husain, and Terry Coatta

To millions of game geeks, the position of QA (quality assurance) tester at Electronic Arts must seem like a dream job. But from the company’s perspective, the overhead associated with QA can look downright frightening, particularly in an era of massively multiplayer games.

Automating Software Failure Reporting:
We can only fix those bugs we know about.

There are many ways to measure quality before and after software is released. For commercial and internal-use-only products, the most important measurement is the user’s perception of product quality. Unfortunately, perception is difficult to measure, so companies attempt to quantify it through customer satisfaction surveys and failure/behavioral data collected from its customer base. This article focuses on the problems of capturing failure data from customer sites.

BASE: An Acid Alternative:
In partitioned databases, trading some consistency for availability can lead to dramatic improvements in scalability.

Web applications have grown in popularity over the past decade. Whether you are building an application for end users or application developers (i.e., services), your hope is most likely that your application will find broad adoption and with broad adoption will come transactional growth. If your application relies upon persistence, then data storage will probably become your bottleneck.

BBR: Congestion-Based Congestion Control:
Measuring bottleneck bandwidth and round-trip propagation time

When bottleneck buffers are large, loss-based congestion control keeps them full, causing bufferbloat. When bottleneck buffers are small, loss-based congestion control misinterprets loss as a signal of congestion, leading to low throughput. Fixing these problems requires an alternative to loss-based congestion control. Finding this alternative requires an understanding of where and how network congestion originates.

BPM: The Promise and the Challenge:
It’s all about closing the loop from conception to execution and back.

Over the last decade, businesses and governments have been giving increasing attention to business processes - to their description, automation, and management. This interest grows out of the need to streamline business operations, consolidate organizations, and save costs, reflecting the fact that the process is the basic unit of business value within an organization.

Barbarians at the Gateways:
High-frequency Trading and Exchange Technology

I am a former high-frequency trader. For a few wonderful years I led a group of brilliant engineers and mathematicians, and together we traded in the electronic marketplaces and pushed systems to the edge of their capability.

Benchmarking "Hello, World!":
Six different views of the execution of "Hello, World!" show what is often missing in today’s tools

As more and more software moves off the desktop and into data centers, and more and more cell phones use server requests as the other half of apps, observation tools for large-scale distributed transaction systems are not keeping up. This makes it tempting to look under the lamppost using simpler tools. You will waste a lot of high-pressure time following that path when you have a sudden complex performance crisis.

Best Practice (BPM):
In business process management, finding the right tool suite is just the beginning.

Just as BPM (business process management) technology is markedly different from conventional approaches to application support, the methodology of BPM development is markedly different from traditional software implementation techniques. With CPI (continuous process improvement) as the core discipline of BPM, the models that drive work through the company evolve constantly. Indeed, recent studies suggest that companies fine-tune their BPM-based applications at least once a quarter (and sometimes as often as eight times per year). The point is that there is no such thing as a "finished" process; it takes multiple iterations to produce highly effective solutions. Every working BPM-based process is just a starting point for the future.

Best Practice: Application Frameworks:
While powerful, frameworks are not for everyone.

While frameworks can be a powerful tool, they have some disadvantages and may not make sense for all organizations. Framework maintainers need to provide standardization and well-defined behavior while not being overly prescriptive. When frameworks strike the right balance, however, they can offer large developer productivity gains. The consistency provided by widespread use of frameworks is a boon for other teams such as SRE and security that have a vested interest in the quality of applications. Additionally, the structure of frameworks provides a foundation for building higher-level abstractions such as microservices platforms, which unlock new opportunities for system architecture and automation.

Best Practices on the Move: Building Web Apps for Mobile Devices:
Which practices should be modified or avoided altogether by developers for the mobile Web?

If it wasn’t your priority last year or the year before, it’s sure to be your priority now: bring your Web site or service to mobile devices in 2013 or suffer the consequences. Early adopters have been talking about mobile taking over since 1999 - anticipating the trend by only a decade or so. Today, mobile Web traffic is dramatically on the rise, and creating a slick mobile experience is at the top of everyone’s mind. Total mobile data traffic is expected to exceed 10 exabytes per month by 2017.

Better Scripts, Better Games:
Smarter, more powerful scripting languages will improve game performance while making gameplay development more efficient.

The video game industry earned $8.85 billion in revenue in 2007, almost as much as movies made at the box office. Much of this revenue was generated by blockbuster titles created by large groups of people. Though large development teams are not unheard of in the software industry, game studios tend to have unique collections of developers. Software engineers make up a relatively small portion of the game development team, while the majority of the team consists of content creators such as artists, musicians, and designers.

Better, Faster, More Secure:
Who’s in charge of the Internet’s future?

Since I started a stint as chair of the IETF in March 2005, I have frequently been asked, “What’s coming next?” but I have usually declined to answer. Nobody is in charge of the Internet, which is a good thing, but it makes predictions difficult. The reason the lack of central control is a good thing is that it has allowed the Internet to be a laboratory for innovation throughout its life—and it’s a rare thing for a major operational system to serve as its own development lab.

Beyond Beowulf Clusters:
As clusters grow in size and complexity, it becomes harder and harder to manage their configurations.

In the early ’90s, the Berkeley NOW Project under David Culler posited that groups of less capable machines could be used to solve scientific and other computing problems at a fraction of the cost of larger computers. In 1994, Donald Becker and Thomas Sterling worked to drive the costs even lower by adopting the then-fledgling Linux operating system to build Beowulf clusters at NASA’s Goddard Space Flight Center. By tying desktop machines together with open source tools such as PVM, MPI, and PBS, early clusters—which were often PC towers stacked on metal shelves with a nest of wires interconnecting them—fundamentally altered the balance of scientific computing.

Beyond Instant Messaging:
Platforms and standards for these services must anticipate and accommodate future developments.

The recent rise in popularity of IM (instant messaging) has driven the development of platforms and the emergence of standards to support IM. Especially as the use of IM has migrated from online socializing at home to business settings, there is a need to provide robust platforms with the interfaces that business customers use to integrate with other work applications. Yet, in the rush to develop a mature IM infrastructure, it is also important to recognize that IM features and uses are still evolving. For example, popular press stories1 have raised the concern that IM interactions may be too distracting in the workplace.

Beyond Page Objects: Testing Web Applications with State Objects:
Use states to drive your tests

End-to-end testing of Web applications typically involves tricky interactions with Web pages by means of a framework such as Selenium WebDriver. The recommended method for hiding such Web-page intricacies is to use page objects, but there are questions to answer first: Which page objects should you create when testing Web applications? What actions should you include in a page object? Which test scenarios should you specify, given your page objects?

Beyond Relational Databases:
There is more to data access than SQL.

The number and variety of computing devices in the environment are increasing rapidly. Real computers are no longer tethered to desktops or locked in server rooms. PDAs, highly mobile tablet and laptop devices, palmtop computers, and mobile telephony handsets now offer powerful platforms for the delivery of new applications and services. These devices are, however, only the tip of the iceberg. Hidden from sight are the many computing and network elements required to support the infrastructure that makes ubiquitous computing possible.

Beyond Server Consolidation:
Server consolidation helps companies improve resource utilization, but virtualization can help in other ways, too.

Virtualization technology was developed in the late 1960s to make more efficient use of hardware. Hardware was expensive, and there was not that much available. Processing was largely outsourced to the few places that did have computers. On a single IBM System/360, one could run in parallel several environments that maintained full isolation and gave each of its customers the illusion of owning the hardware. Virtualization was time sharing implemented at a coarse-grained level, and isolation was the key achievement of the technology.

Beyond the Fix-it Treadmill:
The Use of Post-Incident Artifacts in High-Performing Organizations

Given that humanity’s study of the sociological factors in safety is almost a century old, the technology industry’s post-incident analysis practices and how we create and use the artifacts those practices produce are all still in their infancy. So don’t be surprised that many of these practices are so similar, that the cognitive and social models used to parse apart and understand incidents and outages are few and cemented in the operational ethos, and that the byproducts sought from post-incident analyses are far-and-away focused on remediation items and prevention.

Biases in AI Systems:
A survey for practitioners

This article provides an organization of various kinds of biases that can occur in the AI pipeline starting from dataset creation and problem formulation to data analysis and evaluation. It highlights the challenges associated with the design of bias-mitigation strategies, and it outlines some best practices suggested by researchers. Finally, a set of guidelines is presented that could aid ML developers in identifying potential sources of bias, as well as avoiding the introduction of unwanted biases. The work is meant to serve as an educational resource for ML developers in handling and addressing issues related to bias in AI systems.

Big Games, Small Screens:
Developing 3D games for mobile devices is full of challenges, but the rich, evolving toolset enables some stunning results.

One thing that becomes immediately apparent when creating and distributing mobile 3D games is that there are fundamental differences between the cellphone market and the more traditional games markets, such as consoles and handheld gaming devices. The most striking of these are the number of delivery platforms; the severe constraints of the devices, including small screens whose orientation can be changed; limited input controls; the need to deal with other tasks; the nonphysical delivery mechanism; and the variations in handset performance and input capability.

Bitcoin’s Academic Pedigree:
The concept of cryptocurrencies is built from forgotten ideas in research literature.

We’ve seen repeatedly that ideas in the research literature can be gradually forgotten or lie unappreciated, especially if they are ahead of their time, even in popular areas of research. Both practitioners and academics would do well to revisit old ideas to glean insights for present systems. Bitcoin was unusual and successful not because it was on the cutting edge of research on any of its components, but because it combined old ideas from many previously unrelated fields. This is not easy to do, as it requires bridging disparate terminology, assumptions, etc., but it is a valuable blueprint for innovation.

Bitcoin’s Underlying Incentives:
The unseen economic forces that govern the Bitcoin protocol

Incentives are crucial for the Bitcoin protocol’s security and effectively drive its daily operation. Miners go to extreme lengths to maximize their revenue and often find creative ways to do so that are sometimes at odds with the protocol. Cryptocurrency protocols should be placed on stronger foundations of incentives. There are many areas left to improve, ranging from the very basics of mining rewards and how they interact with the consensus mechanism, through the rewards in mining pools, and all the way to the transaction fee market itself.

Black Box Debugging:
It’s all about what takes place at the boundary of an application.

Modern software development practices build applications as a collection of collaborating components. Unlike older practices that linked compiled components into a single monolithic application, modern executables are made up of any number of executable components that exist as separate binary files. This design means that as an application component needs resources from another component, calls are made to transfer control or data from one component to another. Thus, we can observe externally visible application behaviors by watching the activity that occurs across the boundaries of the application’s constituent components.

Blaster Revisited:
A second look at the cost of Blaster sheds new light on today’s blended threats.

What lessons can we learn from the carnage the Blaster worm created? The following tale is based upon actual circumstances from corporate enterprises that were faced with confronting and eradicating the Blaster worm, which hit in August 2003. The story provides views from many perspectives, illustrating the complexity and sophistication needed to combat new blended threats.

Blockchain Technology: What Is It Good for?:
Industry’s dreams and fears for this new technology

Business executives, government leaders, investors, and researchers frequently ask the following three questions: (1) What exactly is blockchain technology? (2) What capabilities does it provide? (3) What are good applications? Here we answer these questions thoroughly, provide a holistic overview of blockchain technology that separates hype from reality, and propose a useful lexicon for discussing the specifics of blockchain technology in the future.

Blurring Lines Between Hardware and Software:
Software development for embedded systems clearly transcends traditional "programming" and requires intimate knowledge of hardware, as well as deep understanding of the underlying application that is to be implemented.

Motivated by technology leading to the availability of many millions of gates on a chip, a new design paradigm is emerging. This new paradigm allows the integration and implementation of entire systems on one chip.

Borg, Omega, and Kubernetes:
Lessons learned from three container-management systems over a decade

Though widespread interest in software containers is a relatively recent phenomenon, at Google we have been managing Linux containers at scale for more than ten years and built three different container-management systems in that time. Each system was heavily influenced by its predecessors, even though they were developed for different reasons. This article describes the lessons we’ve learned from developing and operating them.

Box Their SOXes Off:
Being proactive with SAS 70 Type II audits helps both parties in a vendor relationship.

Data is a precious resource for any large organization. The larger the organization, the more likely it will rely to some degree on third-party vendors and partners to help it manage and monitor its mission-critical data. In the wake of new regulations for public companies, such as Section 404 of SOX, the folks who run IT departments for Fortune 1000 companies have an ever-increasing need to know that when it comes to the 24/7/365 monitoring of their critical data transactions, they have business partners with well-planned and well-documented procedures. In response to a growing need to validate third-party controls and procedures, some companies are insisting that certain vendors undergo SAS 70 Type II audits.

Breaking the Major Release Habit:
Can agile development make your team more productive?

Keeping up with the rapid pace of change can be a daunting task. Just as you finally get your software working with a new technology to meet yesterday’s requirements, a newer technology is introduced or a new business trend comes along to upset the apple cart. Whether your new challenge is Web services, SOA (service-oriented architecture), ESB (enterprise service bus), AJAX, Linux, the Sarbanes-Oxley Act, distributed development, outsourcing, or competitive pressure, there is an increasing need for development methodologies that help to shorten the development cycle time, respond to user needs faster, and increase quality all at the same time.

Bridging the Object-Relational Divide:
ORM technologies can simplify data access, but be aware of the challenges that come with introducing this new layer of abstraction.

Modern applications are built using two very different technologies: object-oriented programming for business logic; and relational databases for data storage. Object-oriented programming is a key technology for implementing complex systems, providing benefits of reusability, robustness, and maintainability. Relational databases are repositories for persistent data. ORM (object-relational mapping) is a bridge between the two that allows applications to access relational data in an object-oriented way.

Bringing Arbitrary Compute to Authoritative Data:
Many disparate use cases can be satisfied with a single storage system.

While the term ’big data’ is vague enough to have lost much of its meaning, today’s storage systems are growing more quickly and managing more data than ever before. Consumer devices generate large numbers of photos, videos, and other large digital assets. Machines are rapidly catching up to humans in data generation through extensive recording of system logs and metrics, as well as applications such as video capture and genome sequencing. Large data sets are now commonplace, and people increasingly want to run sophisticated analyses on the data.

Broadcast Messaging: Messaging to the Masses:
This powerful form of communication has social implications as well as technical challenges.

We have instantaneous access to petabytes of stored data through Web searches. With respect to messaging, we have an unprecedented number of communication tools that provide both synchronous and asynchronous access to people. E-mail, message boards, newsgroups, IRC (Internet relay chat), and IM (instant messaging) are just a few examples. These tools are all particularly significant because they have become essential productivity entitlements. They have caused a fundamental shift in the way we communicate. Many readers can attest to feeling disconnected when a mail server goes down or when access to IM is unavailable.

Browser Security: Lessons from Google Chrome:
Google Chrome developers focused on three key problems to shield the browser from attacks.

The Web has become one of the primary ways people interact with their computers, connecting people with a diverse landscape of content, services, and applications. Users can find new and interesting content on the Web easily, but this presents a security challenge: malicious Web-site operators can attack users through their Web browsers. Browsers face the challenge of keeping their users safe while providing a rich platform for Web applications.

Bufferbloat: Dark Buffers in the Internet:
Networks without effective AQM may again be vulnerable to congestion collapse.

Today’s networks are suffering from unnecessary latency and poor system performance. The culprit is bufferbloat, the existence of excessively large and frequently full buffers inside the network. Large buffers have been inserted all over the Internet without sufficient thought or testing. They damage or defeat the fundamental congestion-avoidance algorithms of the Internet’s most common transport protocol. Long delays from bufferbloat are frequently attributed incorrectly to network congestion, and this misinterpretation of the problem leads to the wrong solutions being proposed.

Building Collaboration into IDEs:
Edit>Compile>Run>Debug>Collaborate?

Software development is rarely a solo coding effort. More often, it is a collaborative process, with teams of developers working together to design solutions and produce quality code. The members of these close-knit teams often look at one another’s code, collectively make plans about how to proceed, and even fix each other’s bugs when necessary. Teamwork does not stop there, however. An extended team may include project managers, testers, architects, designers, writers, and other specialists, as well as other programming teams.

Building Nutch: Open Source Search:
A case study in writing an open source search engine

Search engines are as critical to Internet use as any other part of the network infrastructure, but they differ from other components in two important ways. First, their internal workings are secret, unlike, say, the workings of the DNS (domain name system). Second, they hold political and cultural power, as users increasingly rely on them to navigate online content.

Building Scalable Web Services:
Build only what you really need.

In the early days of the Web we severely lacked tools and frameworks, and in retrospect it seems noteworthy that those early Web services scaled at all. Nowadays, while the tools have progressed, so too have expectations with respect to richness of interaction, performance, and scalability. In view of these raised expectations it is advisable to build only what you really need, relying on other people’s work where possible. Above all, be cautious in choosing when, what, and how to optimize.

Building Secure Web Applications:
Believe it or not, it’s not a lost cause.

In these days of phishing and near-daily announcements of identity theft via large-scale data losses, it seems almost ridiculous to talk about securing the Web. At this point most people seem ready to throw up their hands at the idea or to lock down one small component that they can control in order to keep the perceived chaos at bay.

Building Systems to Be Shared, Securely:
Want to securely partition VMs? One option is to put ’em in Jail.

The history of computing has been characterized by continuous transformation resulting from the dramatic increases in performance and drops in price described by Moore’s law. Computing power has migrated from centralized mainframes/servers to distributed systems and the commodity desktop. Despite these changes, system sharing remains an important tool for computing. From the multitasking, file-sharing, and virtual machines of the desktop environment to the large-scale sharing of server-class ISP hardware in collocation centers, safely sharing hardware between mutually untrusting parties requires addressing critical concerns of accidental and malicious damage.

Building Systems to Be Shared, Securely:
Want to securely partition VMs? One option is to put ’em in Jail.

The history of computing has been characterized by continuous transformation resulting from the dramatic increases in performance and drops in price described by Moore’s law. Computing power has migrated from centralized mainframes/servers to distributed systems and the commodity desktop. Despite these changes, system sharing remains an important tool for computing. From the multitasking, file-sharing, and virtual machines of the desktop environment to the large-scale sharing of server-class ISP hardware in collocation centers, safely sharing hardware between mutually untrusting parties requires addressing critical concerns of accidental and malicious damage.

C Is Not a Low-level Language:
Your computer is not a fast PDP-11.

In the wake of the recent Meltdown and Spectre vulnerabilities, it’s worth spending some time looking at root causes. Both of these vulnerabilities involved processors speculatively executing instructions past some kind of access check and allowing the attacker to observe the results via a side channel. The features that led to these vulnerabilities, along with several others, were added to let C programmers continue to believe they were programming in a low-level language, when this hasn’t been the case for decades.

CPU DB: Recording Microprocessor History:
With this open database, you can mine microprocessor trends over the past 40 years.

In November 1971, Intel introduced the world’s first single-chip microprocessor, the Intel 4004. It had 2,300 transistors, ran at a clock speed of up to 740 KHz, and delivered 60,000 instructions per second while dissipating 0.5 watts. The following four decades witnessed exponential growth in compute power, a trend that has enabled applications as diverse as climate modeling, protein folding, and computing real-time ballistic trajectories of angry birds.

Cache Me If You Can:
Building a decentralized web-delivery model

The world is more connected than it ever has been before, and with our pocket supercomputers and IoT (Internet of Things) future, the next generation of the web might just be delivered in a peer-to-peer model. It’s a giant problem space, but the necessary tools and technology are here today. We just need to define the problem a little better.

Caching XML Web Services for Mobility:
In the face of unreliable connections and low bandwidth, caching may offer reliable wireless access to Web services.

Web services are emerging as the dominant application on the Internet. The Web is no longer just a repository of information but has evolved into an active medium for providers and consumers of services: Individuals provide peer-to-peer services to access personal contact information or photo albums for other individuals; individuals provide services to businesses for accessing personal preferences or tax information; Web-based businesses provide consumer services such as travel arrangement (Orbitz), shopping (eBay), and e-mail (Hotmail); and several business-to-business (B2B) services such as supply chain management form important applications of the Internet.

Canary Analysis Service:
Automated canarying quickens development, improves production safety, and helps prevent outages.

It is unreasonable to expect engineers working on product development or reliability to have statistical knowledge; removing this hurdle led to widespread CAS adoption. CAS has proven useful even for basic cases that don’t need configuration, and has significantly improved Google’s rollout reliability. Impact analysis shows that CAS has likely prevented hundreds of postmortem-worthy outages, and the rate of postmortems among groups that do not use CAS is noticeably higher.

Certificate Transparency:
Public, verifiable, append-only logs

On August 28, 2011, a mis-issued wildcard HTTPS certificate for google.com was used to conduct a man-in-the-middle attack against multiple users in Iran. The certificate had been issued by a Dutch CA (certificate authority) known as DigiNotar, a subsidiary of VASCO Data Security International. Later analysis showed that DigiNotar had been aware of the breach in its systems for more than a month - since at least July 19. It also showed that at least 531 fraudulent certificates had been issued. The final count may never be known, since DigiNotar did not have records of all the mis-issued certificates.

Challenges of Memory Management on Modern NUMA System:
Optimizing NUMA systems applications with Carrefour

Modern server-class systems are typically built as several multicore chips put together in a single system. Each chip has a local DRAM (dynamic random-access memory) module; together they are referred to as a node. Nodes are connected via a high-speed interconnect, and the system is fully coherent. This means that, transparently to the programmer, a core can issue requests to its node’s local memory as well as to the memories of other nodes. The key distinction is that remote requests will take longer, because they are subject to longer wire delays and may have to jump several hops as they traverse the interconnect.

Closed Source Fights Back:
SCO vs. The World-What Were They Thinking?

In May 2003, the SCO Group, a vendor of the Linux operating system, sent a letter to its customers. Among other things, it stated, "We believe that Linux is, in material part, an unauthorized derivative of Unix." What would make SCO do that?

Cluster-level Logging of Containers with Containers:
Logging Challenges of Container-Based Cloud Deployments

This article shows how cluster-level logging infrastructure can be implemented using open source tools and deployed using the very same abstractions that are used to compose and manage the software systems being logged. Collecting and analyzing log information is an essential aspect of running production systems to ensure their reliability and to provide important auditing information. Many tools have been developed to help with the aggregation and collection of logs for specific software components (e.g., an Apache web server) running on specific servers (e.g., Fluentd and Logstash.)

Code Spelunking Redux:
Is this subject important enough to warrant two articles in five years? I believe it is.

It has been five years since I first wrote about code spelunking, and though systems continue to grow in size and scope, the tools we use to understand those systems are not growing at the same rate. In fact, I believe we are steadily losing ground. So why should we go over the same ground again? Is this subject important enough to warrant two articles in five years? I believe it is.

Code Spelunking: Exploring Cavernous Code Bases:
Code diving through unfamiliar source bases is something we do far more often than write new code from scratch--make sure you have the right gear for the job.

Try to remember your first day at your first software job. Do you recall what you were asked to do, after the human resources people were done with you? Were you asked to write a piece of fresh code? Probably not. It is far more likely that you were asked to fix a bug, or several, and to try to understand a large, poorly documented collection of source code. Of course, this doesn’t just happen to new graduates; it happens to all of us whenever we start a new job or look at a new piece of code. With experience we all develop a set of techniques for working with large, unfamiliar source bases.

Coding Guidelines: Finding the Art in the Science:
What separates good code from great code?

Computer science is both a science and an art. Its scientific aspects range from the theory of computation and algorithmic studies to code design and program architecture. Yet, when it comes time for implementation, there is a combination of artistic flare, nuanced style, and technical prowess that separates good code from great code.

Coding Smart: People vs. Tools:
Tools can help developers be more productive, but they’re no replacement for thinking.

Cool tools are seductive. When we think about software productivity, tools naturally come to mind. When we see pretty new tools, we tend to believe that their amazing features will help us get our work done much faster. Because every software engineer uses software productivity tools daily, and all team managers have to decide which tools their members will use, the latest and greatest look appealing.

Coding for the Code:
Can models provide the DNA for software development?

Despite the considerable effort invested by industry and academia in modeling standards such as UML (Unified Modeling Language), software modeling has long played a subordinate role in commercial software development. Although modeling is generally perceived as state of the art and thus as something that ought to be done, its appreciation seems to pale along with the progression from the early, more conceptual phases of a software project to those where the actual handcrafting is done.

Cognitive Work of Hypothesis Exploration During Anomaly Response:
A look at how we respond to the unexpected

Four incidents from web-based software companies reveal important aspects of anomaly response processes when incidents arise in web operations, two of which are discussed in this article. One particular cognitive function examined in detail is hypothesis generation and exploration, given the impact of obscure automation on engineers’ development of coherent models of the systems they manage. Each case was analyzed using the techniques and concepts of cognitive systems engineering. The set of cases provides a window into the cognitive work "above the line" in incident management of complex web-operation systems.

Collaboration in System Administration:
For sysadmins, solving problems usually involves collaborating with others. How can we make it more effective?

George was in trouble. A seemingly simple deployment was taking all morning, and there seemed no end in sight. His manager kept coming in to check on his progress, as the customer was anxious to have the deployment done. He was supposed to be leaving for a goodbye lunch for a departing co-worker, adding to the stress. He had called in all kinds of help, including colleagues, an application architect, technical support, and even one of the system developers. He used e-mail, instant messaging, face-to-face contacts, his phone, and even his office mate’s phone to communicate with everyone. And George was no novice.

Commercializing Open Source Software:
Many have tried, a few are succeeding, but challenges abound.

The use of open source software has become increasingly popular in production environments, as well as in research and software development. One obvious attraction is the low cost of acquisition. Commercial software has a higher initial cost, though it usually has advantages such as support and training. A number of business models designed by users and vendors combine open source and commercial software; they use open source as much as possible, adding commercial software as needed.

Communications Surveillance: Privacy and Security at Risk:
As the sophistication of wiretapping technology grows, so too do the risks it poses to our privacy and security.

We all know the scene: It is the basement of an apartment building and the lights are dim. The man is wearing a trench coat and a fedora pulled down low to hide his face. Between the hat and the coat we see headphones, and he appears to be listening intently to the output of a set of alligator clips attached to a phone line. He is a detective eavesdropping on a suspect’s phone calls. This is wiretapping. It doesn’t have much to do with modern electronic eavesdropping, which is about bits, packets, switches, and routers.

Compliance Deconstructed:
When you break it down, compliance is largely about ensuring that business processes are executed as expected.

The topic of compliance becomes increasingly complex each year. Dozens of regulatory requirements can affect a company’s business processes. Moreover, these requirements are often vague and confusing. When those in charge of compliance are asked if their business processes are in compliance, it is understandably difficult for them to respond succinctly and with confidence. This article looks at how companies can deconstruct compliance, dealing with it in a systematic fashion and applying technology to automate compliance-related business processes. It also looks specifically at how Microsoft approaches compliance to SOX.

Complying with Compliance:
Blowing it off is not an option.

“Hey, compliance is boring. Really, really boring. And besides, I work neither in the financial industry nor in health care. Why should I care about SOX and HIPAA?” Yep, you’re absolutely right. You write payroll applications, or operating systems, or user interfaces, or (heaven forbid) e-mail servers. Why should you worry about compliance issues?

Componentizing the Web:
We may be on the cusp of a new revolution in web development.

There is no task in software engineering today quite as herculean as web development. A typical specification for a web application might read: The app must work across a wide variety of browsers. It must run animations at 60 fps. It must be immediately responsive to touch. It must conform to a specific set of design principles and specs. It must work on just about every screen size imaginable, from TVs and 30-inch monitors to mobile phones and watch faces. It must be well-engineered and maintainable in the long term.

Computers in Patient Care: The Promise and the Challenge:
Information technology has the potential to radically transform health care. Why has progress been so slow?

A 29-year-old female from New York City comes in at 3 a.m. to an ED (emergency department) in California, complaining of severe acute abdominal pain that woke her up. She reports that she is in California attending a wedding and that she has suffered from similar abdominal pain in the recent past, most recently resulting in an appendectomy. The emergency physician performs an abdominal CAT scan and sees what he believes to be an artifact from the appendectomy in her abdominal cavity. He has no information about the patient’s past history other than what she is able to tell him; he has no access to any images taken before or after the appendectomy, nor does he have any other vital information about the surgical operative note or follow-up.

Computing without Processors:
Heterogeneous systems allow us to target our programming to the appropriate environment.

From the programmer’s perspective the distinction between hardware and software is being blurred. As programmers struggle to meet the performance requirements of today’s systems, they will face an ever increasing need to exploit alternative computing elements such as GPUs (graphics processing units), which are graphics cards subverted for data-parallel computing, and FPGAs (field-programmable gate arrays), or soft hardware.

Condos and Clouds:
Constraints in an environment empower the services.

Living in a condominium has its constraints and its services. By defining the lifestyle and limits on usage patterns, it is possible to pack many homes close together and to provide the residents with many conveniences. Condo living can offer a great value to those interested and willing to live within its constraints and enjoy the sharing of common services.

Containers Will Not Fix Your Broken Culture (and Other Hard Truths):
Complex socio-technical systems are hard; film at 11.

We focus so often on technical anti-patterns, neglecting similar problems inside our social structures. Spoiler alert: the solutions to many difficulties that seem technical can be found by examining our interactions with others. Let’s talk about five things you’ll want to know when working with those pesky creatures known as humans.

Continuous Delivery Sounds Great, but Will It Work Here?:
It’s not magic, it just requires continuous, daily improvement at all levels.

Continuous delivery is a set of principles, patterns, and practices designed to make deployments predictable, routine affairs that can be performed on demand at any time. This article introduces continuous delivery, presents both common objections and actual obstacles to implementing it, and describes how to overcome them using real-life examples. Continuous delivery is not magic. It’s about continuous, daily improvement at all levels of the organization.

Controlling Queue Delay:
A modern AQM is just one piece of the solution to bufferbloat.

Nearly three decades after it was first diagnosed, the "persistently full buffer problem" recently exposed as part of "bufferbloat", is still with us and made increasingly critical by two trends. First, cheap memory and a "more is better" mentality have led to the inflation and proliferation of buffers. Second, dynamically varying path characteristics are much more common today and are the norm at the consumer Internet edge. Reasonably sized buffers become extremely oversized when link rates and path delays fall below nominal values.

Cooling the Data Center:
What can be done to make cooling systems in data centers more energy efficient?

Power generation accounts for about 40 to 45 percent of the primary energy supply in the US and the UK, and a good fraction is used to heat, cool, and ventilate buildings. A new and growing challenge in this sector concerns computer data centers and other equipment used to cool computer data systems. On the order of 6 billion kilowatt hours of power was used in data centers in 2006 in the US, representing about 1.5 percent of the country’s electricity consumption.

Corp to Cloud: Google’s Virtual Desktops:
How Google moved its virtual desktops to the cloud

Over one-fourth of Googlers use internal, data-center-hosted virtual desktops. This on-premises offering sits in the corporate network and allows users to develop code, access internal resources, and use GUI tools remotely from anywhere in the world. Among its most notable features, a virtual desktop instance can be sized according to the task at hand, has persistent user storage, and can be moved between corporate data centers to follow traveling Googlers. Until recently, our virtual desktops were hosted on commercially available hardware on Google’s corporate network using a homegrown open-source virtual cluster-management system called Ganeti. Today, this substantial and Google-critical workload runs on GCP (Google Compute Platform).

Crash Consistency:
Rethinking the Fundamental Abstractions of the File System

The reading and writing of data, one of the most fundamental aspects of any Von Neumann computer, is surprisingly subtle and full of nuance. For example, consider access to a shared memory in a system with multiple processors. While a simple and intuitive approach known as strong consistency is easiest for programmers to understand, many weaker models are in widespread use (e.g., x86 total store ordering); such approaches improve system performance, but at the cost of making reasoning about system behavior more complex and error-prone.

Creating Languages in Racket:
Sometimes you just have to make a better mousetrap.

Choosing the right tool for a simple job is easy: a screwdriver is usually the best option when you need to change the battery in a toy, and grep is the obvious choice to check for a word in a text document. For more complex tasks, the choice of tool is rarely so straightforward--all the more so for a programming task, where programmers have an unparalleled ability to construct their own tools. Programmers frequently solve programming problems by creating new tool programs, such as scripts that generate source code from tables of data.

Criminal Code: The Making of a Cybercriminal:
A fictional account of malware creators and their experiences

This is a fictional account of malware creators and their experiences. Although the characters are made up, the techniques and events are patterned on real activities of many different groups developing malicious software. “Make some money!” Misha’s father shouted. “You spent all that time for a stupid contest and where did it get you? Nowhere! You have no job and you didn’t even win! You need to stop playing silly computer games and earn some money!”

Culture Surprises in Remote Software Development Teams:
When in Rome doesn’t help when your team crosses time zones, and your deadline doesn’t.

Technology has made it possible for organizations to construct teams of people who are not in the same location, adopting what one company calls "virtual collocation." Worldwide groups of software developers, financial analysts, automobile designers, consultants, pricing analysts, and researchers are examples of teams that work together from disparate locations, using a variety of collaboration technologies that allow communication across space and time.

Cybercrime 2.0: When the Cloud Turns Dark:
Web-based malware attacks are more insidious than ever. What can be done to stem the tide?

As the Web has become vital for day-to-day transactions, it has also become an attractive avenue for cybercrime. Financially motivated, the crime we see on the Web today is quite different from the more traditional network attacks. A few years ago Internet attackers relied heavily on remotely exploiting servers identified by scanning the Internet for vulnerable network services. Autonomously spreading computer worms such as Code Red and SQLSlammer were examples of such scanning attacks. Their huge scale put even the Internet at large at risk; for example, SQLSlammer generated traffic sufficient to melt down backbones.

Cybercrime: An Epidemic:
Who commits these crimes, and what are their motivations?

Painted in the broadest of strokes, cybercrime essentially is the leveraging of information systems and technology to commit larceny, extortion, identity theft, fraud, and, in some cases, corporate espionage. Who are the miscreants who commit these crimes, and what are their motivations? One might imagine they are not the same individuals committing crimes in the physical world. Bank robbers and scam artists garner a certain public notoriety after only a few occurrences of their crimes, yet cybercriminals largely remain invisible and unheralded. Based on sketchy news accounts and a few public arrests, such as Mafiaboy, accused of paralyzing Amazon, CNN, and other Web sites, the public may infer these miscreants are merely a subculture of teenagers.

DAFS: A New High-Performance Networked File System:
This emerging file-access protocol dramatically enhances the flow of data over a network, making life easier in the data center.

The Direct Access File System (DAFS) is a remote file-access protocol designed to take advantage of new high-throughput, low-latency network technology.

DNS Complexity:
Although it contains just a few simple rules, DNS has grown into an enormously complex system.

DNS is a distributed, coherent, reliable, autonomous, hierarchical database, the first and only one of its kind. Created in the 1980s when the Internet was still young but overrunning its original system for translating host names into IP addresses, DNS is one of the foundation technologies that made the worldwide Internet possible. Yet this did not all happen smoothly, and DNS technology has been periodically refreshed and refined. Though it’s still possible to describe DNS in simple terms, the underlying details are by now quite sublime.

DSL for the Uninitiated:
Domain-specific languages bridge the semantic gap in programming.

One of the main reasons why software projects fail is the lack of communication between the business users, who actually know the problem domain, and the developers who design and implement the software model. Business users understand the domain terminology, and they speak a vocabulary that may be quite alien to the software people; it’s no wonder that the communication model can break down right at the beginning of the project life cycle.

DSPs: Back to the Future:
To understand where DSPs are headed, we must look at where they’ve come from.

From the dawn of the DSP (digital signal processor), an old quote still echoes: "Oh, no! We’ll have to use state-of-the-art 5µm NMOS!" The speaker’s name is lost in the fog of history, as are many things from the ancient days of 5µm chip design. This quote refers to the first Bell Labs DSP whose mask set in fact underwent a 10 percent linear lithographic shrink to 4.5µm NMOS (N-channel metal oxide semiconductor) channel length and taped out in late 1979 with an aggressive full-custom circuit design.

Dark Patterns: Past, Present, and Future:
The evolution of tricky user interfaces

Dark patterns are an abuse of the tremendous power that designers hold in their hands. As public awareness of dark patterns grows, so does the potential fallout. Journalists and academics have been scrutinizing dark patterns, and the backlash from these exposures can destroy brand reputations and bring companies under the lenses of regulators. Design is power. In the past decade, software engineers have had to confront the fact that the power they hold comes with responsibilities to users and to society. In this decade, it is time for designers to learn this lesson as well.

Data Sketching:
The approximate approach is often faster and more efficient.

Do you ever feel overwhelmed by an unending stream of information? It can seem like a barrage of new email and text messages demands constant attention, and there are also phone calls to pick up, articles to read, and knocks on the door to answer. Putting these pieces together to keep track of what’s important can be a real challenge. In response to this challenge, the model of streaming data processing has grown in popularity. The aim is no longer to capture, store, and index every minute event, but rather to process each observation quickly in order to create a summary of the current state.

Data in Flight:
How streaming SQL technology can help solve the Web 2.0 data crunch.

Web applications produce data at colossal rates, and those rates compound every year as the Web becomes more central to our lives. Other data sources such as environmental monitoring and location-based services are a rapidly expanding part of our day-to-day experience. Even as throughput is increasing, users and business owners expect to see their data with ever-decreasing latency. Advances in computer hardware (cheaper memory, cheaper disks, and more processing cores) are helping somewhat, but not enough to keep pace with the twin demands of rising throughput and decreasing latency.

Data on the Outside vs. Data on the Inside:
Data kept outside SQL has different characteristics from data kept inside.

This article describes the impact of services and trust on the treatment of data. It introduces the notions of inside data as distinct from outside data. After discussing the temporal implications of not sharing transactions across the boundaries of services, the article considers the need for immutability and stability in outside data. This leads to a depiction of outside data as a DAG of data items being independently generated by disparate services.

Data-Parallel Computing:
Data parallelism is a key concept in leveraging the power of today’s manycore GPUs.

Users always care about performance. Although often it’s just a matter of making sure the software is doing only what it should, there are many cases where it is vital to get down to the metal and leverage the fundamental characteristics of the processor.

Databases of Discovery:
Open-ended database ecosystems promote new discoveries in biotech. Can they help your organization, too?

The National Center for Biotechnology Information is responsible for massive amounts of data. A partial list includes the largest public bibliographic database in biomedicine, the U.S. national DNA sequence database, an online free full text research article database, assembly, annotation, and distribution of a reference set of genes, genomes, and chromosomes, online text search and retrieval systems, and specialized molecular biology data search engines. At this writing, NCBI receives about 50 million Web hits per day, at peak rates of about 1,900 hits per second, and about 400,000 BLAST searches per day from about 2.5 million users.

Death by UML Fever:
Self-diagnosis and early treatment are crucial in the fight against UML Fever.

A potentially deadly illness, clinically referred to as UML (Unified Modeling Language) fever, is plaguing many software-engineering efforts today. This fever has many different strains that vary in levels of lethality and contagion. A number of these strains are symptomatically related, however. Rigorous laboratory analysis has revealed that each is unique in origin and makeup. A particularly insidious characteristic of UML fever, common to most of its assorted strains, is the difficulty individuals and organizations have in self-diagnosing the affliction. A consequence is that many cases of the fever go untreated and often evolve into more complex and lethal strains.

Debugging Distributed Systems:
Challenges and options for validation and debugging

Distributed systems pose unique challenges for software developers. Reasoning about concurrent activities of system nodes and even understanding the system’s communication topology can be difficult. A standard approach to gaining insight into system activity is to analyze system logs. Unfortunately, this can be a tedious and complex process. This article looks at several key features and debugging challenges that differentiate distributed systems from other kinds of software. The article presents several promising tools and ongoing research to help resolve these challenges.

Debugging Incidents in Google’s Distributed Systems:
How experts debug production issues in complex distributed systems

This article covers the outcomes of research performed in 2019 on how engineers at Google debug production issues, including the types of tools, high-level strategies, and low-level tasks that engineers use in varying combinations to debug effectively. It examines the research approach used to capture data, summarizing the common engineering journeys for production investigations and sharing examples of how experts debug complex distributed systems. Finally, the article extends the Google specifics of this research to provide some practical strategies that you can apply in your organization.

Debugging in an Asynchronous World:
Hard-to-track bugs can emerge when you can’t guarantee sequential execution. The right tools and the right techniques can help.

Pagers, cellular phones, smart appliances, and Web services - these products and services are almost omnipresent in our world, and are stimulating the creation of a new breed of software: applications that must deal with inputs from a variety of sources, provide real-time responses, deliver strong security - and do all this while providing a positive user experience. In response, a new style of application programming is taking hold, one that is based on multiple threads of control and the asynchronous exchange of data, and results in fundamentally more complex applications.

Decentralizing SIP:
If you’re looking for a low-maintenance IP communications network, peer-to-peer SIP might be just the thing.

SIP (Session Initiation Protocol) is the most popular protocol for VoIP in use today.1 It is widely used by enterprises, consumers, and even carriers in the core of their networks. Since SIP is designed for establishing media sessions of any kind, it is also used for a variety of multimedia applications beyond VoIP, including IPTV, videoconferencing, and even collaborative video gaming.

Declarative Machine Learning Systems:
The future of machine learning will depend on it being in the hands of the rest of us.

The people training and using ML models now are typically experienced developers with years of study working within large organizations, but the next wave of ML systems should allow a substantially larger number of people, potentially without any coding skills, to perform the same tasks. These new ML systems will not require users to fully understand all the details of how models are trained and used for obtaining predictions, but will provide them a more abstract interface that is less demanding and more familiar.

Demystifying Stablecoins:
Cryptography meets monetary policy

Self-sovereign stablecoins are interesting and probably here to stay; however, they face numerous regulatory hurdles from banking, financial tracking, and securities laws. For stablecoins backed by a governmental currency, the ultimate expression would be a CBDC. Since paper currency has been in steady decline (and disproportionately for legitimate transactions), a CBDC could reintroduce cash with technological advantages and efficient settlement while minimizing user fees.

Describing the Elephant: The Different Faces of IT as Service:
Terms such as grid, on-demand, and service-oriented architecture are mired in confusion, but there is an overarching trend behind them all.

In a well-known fable, a group of blind men are asked to describe an elephant. Each encounters a different part of the animal and, not surprisingly, provides a different description. We see a similar degree of confusion in the IT industry today, as terms such as service-oriented architecture, grid, utility computing, on-demand, adaptive enterprise, data center automation, and virtualization are bandied about. As when listening to the blind men, it can be difficult to know what reality lies behind the words, whether and how the different pieces fit together, and what we should be doing about the animal(s) that are being described.

Design Exploration through Code-generating DSLs:
High-level DSLs for low-level programming

DSLs (domain-specific languages) make programs shorter and easier to write. They can be stand-alone - for example, LaTeX, Makefiles, and SQL - or they can be embedded in a host language. You might think that DSLs embedded in high-level languages would be abstract or mathematically oriented, far from the nitty-gritty of low-level programming. This is not the case. This article demonstrates how high-level EDSLs (embedded DSLs) really can ease low-level programming. There is no contradiction.

Designing Cluster Schedulers for Internet-Scale Services:
Embracing failures for improving availability

Engineers looking to build scheduling systems should consider all failure modes of the underlying infrastructure they use and consider how operators of scheduling systems can configure remediation strategies, while aiding in keeping tenant systems as stable as possible during periods of troubleshooting by the owners of the tenant systems.

Designing Portable Collaborative Networks:
A middleware solution to keep pace with the ever-changing ways in which mobile workers collaborate.

Peer-to-peer technology and wireless networking offer great potential for working together away from the desk - but they also introduce unique software and infrastructure challenges. The traditional idea of the work environment is anchored to a central location - the desk and office - where the resources needed for the job are located.

Designing UIs for Static Analysis Tools:
Evaluating tool design guidelines with SWAN

Static-analysis tools suffer from usability issues such as a high rate of false positives, lack of responsiveness, and unclear warning descriptions and classifications. Here, we explore the effect of applying user-centered approach and design guidelines to SWAN, a security-focused static-analysis tool for the Swift programming language. SWAN is an interesting case study for exploring static-analysis tool usability because of its large target audience, its potential to integrate easily into developers' workflows, and its independence from existing analysis platforms.

Desktop Linux: Where Art Thou?:
Catching up, meeting new challenges, moving ahead

Linux on the desktop has come a long way - and it’s been a roller-coaster ride. At the height of the dot-com boom, around the time of Red Hat’s initial public offering, people expected Linux to take off on the desktop in short order. A few years later, after the stock market crash and the failure of a couple of high-profile Linux companies, pundits were quick to proclaim the stillborn death of Linux on the desktop.

DevOps Metrics:
Your biggest mistake might be collecting the wrong data.

Delivering value to the business through software requires processes and coordination that often span multiple teams across complex systems, and involves developing and delivering software with both quality and resiliency. As practitioners and professionals, we know that software development and delivery is an increasingly difficult art and practice, and that managing and improving any process or system requires insights into that system. Therefore, measurement is paramount to creating an effective software value stream. Yet accurate measurement is no easy feat.

Digging into Big Provenance (with SPADE):
A user interface for querying provenance

Several interfaces exist for querying provenance. Many are not flexible in allowing users to select a database type of their choice. Some provide query functionality in a data model that is different from the graph-oriented one that is natural for provenance. Others have intuitive constructs for finding results but have limited support for efficiently chaining responses, as needed for faceted search. This article presents a user interface for querying provenance that addresses these concerns and is agnostic to the underlying database being used.

Digitally Assisted Analog Integrated Circuits:
Closing the gap between analog and digital

In past decades, “Moore’s law”1 has governed the revolution in microelectronics. Through continuous advancements in device and fabrication technology, the industry has maintained exponential progress rates in transistor miniaturization and integration density. As a result, microchips have become cheaper, faster, more complex, and more power efficient.

Disambiguating Databases:
Use the database built for your access model.

The topic of data storage is one that doesn’t need to be well understood until something goes wrong (data disappears) or something goes really right (too many customers). Because databases can be treated as black boxes with an API, their inner workings are often overlooked. They’re often treated as magic things that just take data when offered and supply it when asked. Since these two operations are the only understood activities of the technology, they are often the only features presented when comparing different technologies.

Discrimination in Online Ad Delivery:
Google ads, black names and white names, racial discrimination, and click advertising

Do online ads suggestive of arrest records appear more often with searches of black-sounding names than white-sounding names? What is a black-sounding name or white-sounding name, anyway? How many more times would an ad have to appear adversely affecting one racial group for it to be considered discrimination? Is online activity so ubiquitous that computer scientists have to think about societal consequences such as structural racism in technology design? If so, how is this technology to be built? Let’s take a scientific dive into online ad delivery to find answers.

Disks from the Perspective of a File System:
Disks lie. And the controllers that run them are partners in crime.

Most applications do not deal with disks directly, instead storing their data in files in a file system, which protects us from those scoundrel disks. After all, a key task of the file system is to ensure that the file system can always be recovered to a consistent state after an unplanned system crash (for example, a power failure). While a good file system will be able to beat the disks into submission, the required effort can be great and the reduced performance annoying.

Dismantling the Barriers to Entry:
We have to choose to build a web that is accessible to everyone.

A war is being waged in the world of web development. On one side is a vanguard of toolmakers and tool users, who thrive on the destruction of bad old ideas ("old," in this milieu, meaning anything that debuted on Hacker News more than a month ago) and raucous debates about transpilers and suchlike.

Distributed Computing Economics:
Computing economics are changing. Today there is rough price parity between: (1) one database access; (2) 10 bytes of network traffic; (3) 100,000 instructions; (4) 10 bytes of disk storage; and (5) a megabyte of disk bandwidth. This has implications for how one structures Internet-scale distributed computing: one puts computing as close to the data as possible in order to avoid expensive network traffic.

Computing is free. The world’s most powerful computer is free ([email protected] is a 54-teraflop machine). Google freely provides a trillion searches per year to the world’s largest online database (two petabytes). Hotmail freely carries a trillion e-mail messages per year. Amazon.com offers a free book-search tool. Many sites offer free news and other free content. Movies, sports events, concerts, and entertainment are freely available via television.

Distributed Development: Lessons Learned:
Why repeat the mistakes of the past if you don’t have to?

Delivery of a technology-based project is challenging, even under well-contained, familiar circumstances. And a tight-knit team can be a major factor in success. It is no mystery, therefore, why most small, new technology teams opt to work in a garage (at times literally). Keeping the focus of everyone’s energy on the development task at hand means a minimum of non-engineering overhead.

Division of Labor in Embedded Systems:
You can choose among several strategies for partitioning an embedded application over incoherent processor cores. Here’s practical advice on the advantages and pitfalls of each.

Increasingly, embedded applications require more processing power than can be supplied by a single processor, even a heavily pipelined one that uses a high-performance architecture such as very long instruction word (VLIW) or superscalar. Simply driving up the clock is often prohibitive in the embedded world because higher clocks require proportionally more power, a commodity often scarce in embedded systems. Multiprocessing, where the application is run on two or more processors concurrently, is the natural route to ever more processor cycles within a fixed power budget.

Document & Media Exploitation:
The DOMEX challenge is to turn digital bits into actionable intelligence.

A computer used by Al Qaeda ends up in the hands of a Wall Street Journal reporter. A laptop from Iran is discovered that contains details of that country’s nuclear weapons program. Photographs and videos are downloaded from terrorist Web sites. As evidenced by these and countless other cases, digital documents and storage devices hold the key to many ongoing military and criminal investigations. The most straightforward approach to using these media and documents is to explore them with ordinary tools—open the word files with Microsoft Word, view the Web pages with Internet Explorer, and so on.

Domain-specific Languages and Code Synthesis Using Haskell:
Looking at embedded DSLs

There are many ways to give instructions to a computer: an electrical engineer might write a MATLAB program; a database administrator might write an SQL script; a hardware engineer might write in Verilog; and an accountant might write a spreadsheet with embedded formulas. Aside from the difference in language used in each of these examples, there is an important difference in form and idiom. Each uses a language customized to the job at hand, and each builds computational requests in a form both familiar and productive for programmers (although accountants may not think of themselves as programmers).

Don’t Settle for Eventual Consistency:
Stronger properties for low-latency geo-replicated storage

Geo-replicated storage provides copies of the same data at multiple, geographically distinct locations. Facebook, for example, geo-replicates its data (profiles, friends lists, likes, etc.) to data centers on the east and west coasts of the United States, and in Europe. In each data center, a tier of separate Web servers accepts browser requests and then handles those requests by reading and writing data from the storage system.

Dynamics of Change: Why Reactivity Matters:
Tame the dynamics of change by centralizing each concern in its own module.

Professional programming is about dealing with software at scale. Everything is trivial when the problem is small and contained: it can be elegantly solved with imperative programming or functional programming or any other paradigm. Real-world challenges arise when programmers have to deal with large amounts of data, network requests, or intertwined entities, as in UI (user interface) programming.

E-mail Authentication: What, Why, How?:
Perhaps we should have figured out what was going to happen when Usenet started to go bad.

Internet e-mail was conceived in a different world than we live in today. It was a small, tightly knit community, and we didn’t really have to worry too much about miscreants. Generally, if someone did something wrong, the problem could be dealt with through social means; “shunning” is very effective in small communities. Perhaps we should have figured out what was going to happen when Usenet started to go bad. Usenet was based on an inexpensive network called UUCP, which was fairly easy to join, so it gave us a taste of what happens when the community becomes larger and more distributed—and harder to manage.

Enclaves in the Clouds:
Legal considerations and broader implications

With organizational data practices coming under increasing scrutiny, demand is growing for mechanisms that can assist organizations in meeting their data-management obligations. TEEs (trusted execution environments) provide hardware-based mechanisms with various security properties for assisting computation and data management. TEEs are concerned with the confidentiality and integrity of data, code, and the corresponding computation. Because the main security properties come from hardware, certain protections and guarantees can be offered even if the host privileged software stack is vulnerable.

Energy Management on Handheld Devices:
Whatever their origin, all handheld devices share the same Achilles heel: the battery.

Handheld devices are becoming ubiquitous and as their capabilities increase, they are starting to displace laptop computers - much as laptop computers have displaced desktop computers in many roles. Handheld devices are evolving from today’s PDAs, organizers, cellular phones, and game machines into a variety of new forms. Although partially offset by improvements in low-power electronics, this increased functionality carries a corresponding increase in energy consumption. Second, as a consequence of displacing other pieces of equipment, handheld devices are seeing more use between battery charges. Finally, battery technology is not improving at the same pace as the energy requirements of handheld electronics.

Enhanced Debugging with Traces:
An essential technique used in emulator development is a useful addition to any programmer’s toolbox.

Creating an emulator to run old programs is a difficult task. You need a thorough understanding of the target hardware and the correct functioning of the original programs that the emulator is to execute. In addition to being functionally correct, the emulator must hit a performance target of running the programs at their original realtime speed. Reaching these goals inevitably requires a considerable amount of debugging. The bugs are often subtle errors in the emulator itself but could also be a misunderstanding of the target hardware or an actual known bug in the original program. (It is also possible the binary data for the original program has become subtly corrupted or is not the version expected.)

Enterprise Grid Computing:
Grid computing holds great promise for the enterprise data center, but many technical and operational hurdles remain.

I have to admit a great measure of sympathy for the IT populace at large, when it is confronted by the barrage of hype around grid technology, particularly within the enterprise. Individual vendors have attempted to plant their flags in the notionally virgin technological territory and proclaim it as their own, using terms such as grid, autonomic, self-healing, self-managing, adaptive, utility, and so forth. Analysts, well, analyze and try to make sense of it all, and in the process each independently creates his or her own map of this terra incognita, naming it policy-based computing, organic computing, and so on. Unfortunately, this serves only to further muddy the waters for most people.

Enterprise SSDs:
Solid-state drives are finally ready for the enterprise. But beware, not all SSDs are created alike.

For designers of enterprise systems, ensuring that hardware performance keeps pace with application demands is a mind-boggling exercise. The most troubling performance challenge is storage I/O. Spinning media, while exceptional in scaling areal density, will unfortunately never keep pace with I/O requirements. The most cost-effective way to break through these storage I/O limitations is by incorporating high-performance SSDs (solid-state drives) into the systems.

Enterprise Search: Tough Stuff:
Why is it that searching an intranet is so much harder than searching the Web?

The last decade has witnessed the growth of information retrieval from a boutique discipline in information and library science to an everyday experience for billions of people around the world. This revolution has been driven in large measure by the Internet, with vendors focused on search and navigation of Web resources and Web content management. Simultaneously, enterprises have invested in networking all of their information together to the point where it is increasingly possible for employees to have a single window into the enterprise.

Enterprise Software as Service:
Online services are changing the nature of software.

While the practice of outsourcing business functions such as payroll has been around for decades, its realization as online software services has only recently become popular. In the online service model, a provider develops an application and operates the servers that host it. Customers access the application over the Internet using industry-standard browsers or Web services clients. A wide range of online applications, including e-mail, human resources, business analytics, CRM (customer relationship management), and ERP (enterprise resource planning), are available.

Enterprise-Grade Wireless:
Wireless technology has come a long way, but is it robust enough for today’s enterprise?

We have been working in the wireless space in one form or another in excess of 10 years and have participated in every phase of its maturation process. We saw wireless progress from a toy technology before the dot-com boom, to something truly promising during the boom, only to be left wanting after the bubble when the technology was found to be not ready for prime time. Fortunately, it appears that we have finally reached the point where the technology and the enterprise’s expectations have finally converged.

Erlang for Concurrent Programming:
What role can programming languages play in dealing with concurrency? One answer can be found in Erlang, a language designed for concurrency from the ground up.

Erlang is a language developed to let mere mortals write, test, deploy, and debug fault-tolerant concurrent software. Developed at the Swedish telecom company Ericsson in the late 1980s, it started as a platform for developing soft realtime software for managing phone switches. It has since been open-sourced and ported to several common platforms, finding a natural fit not only in distributed Internet server applications, but also in graphical user interfaces and ordinary batch applications.

Error Messages:
What’s the Problem?

Computer users spend a lot of time chasing down errors - following the trail of clues that starts with an error message and that sometimes leads to a solution and sometimes to frustration. Problems with error messages are particularly acute for system administrators (sysadmins) - those who configure, install, manage, and maintain the computational infrastructure of the modern world - as they spend a lot of effort to keep computers running amid errors and failures.

Eventual Consistency Today: Limitations, Extensions, and Beyond:
How can applications be built on eventually consistent infrastructure given no guarantee of safety?

In a July 2000 conference keynote, Eric Brewer, now VP of engineering at Google and a professor at the University of California, Berkeley, publicly postulated the CAP (consistency, availability, and partition tolerance) theorem, which would change the landscape of how distributed storage systems were architected. Brewer’s conjecture--based on his experiences building infrastructure for some of the first Internet search engines at Inktomi--states that distributed systems requiring always-on, highly available operation cannot guarantee the illusion of coherent, consistent single-system operation in the presence of network partitions, which cut communication between active servers.

Eventually Consistent:
Building reliable distributed systems at a worldwide scale demands trade-offs?between consistency and availability.

At the foundation of Amazon’s cloud computing are infrastructure services such as Amazon’s S3 (Simple Storage Service), SimpleDB, and EC2 (Elastic Compute Cloud) that provide the resources for constructing Internet-scale computing platforms and a great variety of applications. The requirements placed on these infrastructure services are very strict; they need to score high marks in the areas of security, scalability, availability, performance, and cost effectiveness, and they need to meet these requirements while serving millions of customers around the globe, continuously.

Eventually Consistent: Not What You Were Expecting?:
Methods of quantifying consistency (or lack thereof) in eventually consistent storage systems

Storage systems continue to lay the foundation for modern Internet services such as Web search, e-commerce, and social networking. Pressures caused by rapidly growing user bases and data sets have driven system designs away from conventional centralized databases and toward more scalable distributed solutions, including simple NoSQL key-value storage systems, as well as more elaborate NewSQL databases that support transactions at scale.

Everything VPN is New Again:
The 24-year-old security model has found a second wind.

The VPN (virtual private network) is 24 years old. The concept was created for a radically different Internet from the one we know today. As the Internet grew and changed, so did VPN users and applications. The VPN had an awkward adolescence in the Internet of the 2000s, interacting poorly with other widely popular abstractions. In the past decade the Internet has changed again, and this new Internet offers new uses for VPNs. The development of a radically new protocol, WireGuard, provides a technology on which to build these new VPNs.

Evolution and Practice: Low-latency Distributed Applications in Finance:
The finance industry has unique demands for low-latency distributed systems.

Virtually all systems have some requirements for latency, defined here as the time required for a system to respond to input. Latency requirements appear in problem domains as diverse as aircraft flight controls, voice communications, multiplayer gaming, online advertising, and scientific experiments. Distributed systems present special latency considerations. In recent years the automation of financial trading has driven requirements for distributed systems with challenging latency requirements and global geographic distribution. Automated trading provides a window into the engineering challenges of ever-shrinking latency requirements, which may be useful to software engineers in other fields.

Evolution of the Product Manager:
Better education needed to develop the discipline

Software practitioners know that product management is a key piece of software development. Product managers talk to users to help figure out what to build, define requirements, and write functional specifications. They work closely with engineers throughout the process of building software. They serve as a sounding board for ideas, help balance the schedule when technical challenges occur - and push back to executive teams when technical revisions are needed. Product managers are involved from before the first code is written, until after it goes out the door.

Exposing the ORM Cache:
Familiarity with ORM caching issues can help prevent performance problems and bugs.

In the early 1990s, when object-oriented languages emerged into the mainstream of software development, a noticeable surge in productivity occurred as developers saw new and better ways to create software programs. Although the new and efficient object programming paradigm was hailed and accepted by a growing number of organizations, relational database management systems remained the preferred technology for managing enterprise data. Thus was born ORM (object-relational mapping), out of necessity, and the complex challenge of saving the persistent state of an object environment in a relational database subsequently became known as the object-relational impedance mismatch.

Extending the Semantics of Scheduling Priorities:
Increasing parallelism demands new paradigms.

Application performance is directly affected by the hardware resources that the application requires, the degree to which such resources are available, and how the operating system addresses its requirements with regard to the other processes in the system. Ideally, an application would have access to all the resources it could use and be allowed to complete its work without competing with any other activity in the system. In a world of highly shared hardware resources and generalpurpose, time-share-based operating systems, however, no guarantees can be made as to how well resourced an application will be.

Extensible Programming for the 21st Century:
Is an open, more flexible programming environment just around the corner?

In his keynote address at OOPSLA ’98, Sun Microsystems Fellow Guy L. Steele Jr. said, “From now on, a main goal in designing a language should be to plan for growth.” Functions, user-defined types, operator overloading, and generics (such as C++ templates) are no longer enough: tomorrow’s languages must allow programmers to add entirely new kinds of information to programs, and control how it is processed. This article argues that next-generation programming systems can accomplish this by combining three specific technologies.

Extreme Software Scaling:
Chip multiprocessors have introduced a new dimension in scaling for application developers, operating system designers, and deployment specialists.

The advent of SMP (symmetric multiprocessing) added a new degree of scalability to computer systems. Rather than deriving additional performance from an incrementally faster microprocessor, an SMP system leverages multiple processors to obtain large gains in total system performance. Parallelism in software allows multiple jobs to execute concurrently on the system, increasing system throughput accordingly. Given sufficient software parallelism, these systems have proved to scale to several hundred processors.

FPGA Programming for the Masses:
The programmability of FPGAs must improve if they are to be part of mainstream computing.

When looking at how hardware influences computing performance, we have GPPs (general-purpose processors) on one end of the spectrum and ASICs (application-specific integrated circuits) on the other. Processors are highly programmable but often inefficient in terms of power and performance. ASICs implement a dedicated and fixed function and provide the best power and performance characteristics, but any functional change requires a complete (and extremely expensive) re-spinning of the circuits.

Fail at Scale:
Reliability in the face of rapid change

Failure is part of engineering any large-scale system. One of Facebook’s cultural values is embracing failure. This can be seen in the posters hung around the walls of our Menlo Park headquarters: "What Would You Do If You Weren’t Afraid?" and "Fortune Favors the Bold."

Faucet: Deploying SDN in the Enterprise:
Using OpenFlow and DevOps for rapid development

While SDN as a technology continues to evolve and become even more programmable, Faucet and OpenFlow 1.3 hardware together are sufficient to realize benefits today. This article describes specifically how to take advantage of DevOps practices to develop and deploy features rapidly. It also describes several practical deployment scenarios, including firewalling and network function virtualization.

Fault Injection in Production:
Making the case for resilience testing

When we build Web infrastructures at Etsy, we aim to make them resilient. This means designing them carefully so that they can sustain their (increasingly critical) operations in the face of failure. Thankfully, there have been a couple of decades and reams of paper spent on researching how fault tolerance and graceful degradation can be brought to computer systems. That helps the cause.

Fighting Physics: A Tough Battle:
Thinking of doing IPC over the long haul? Think again. The laws of physics say you’re hosed.

Over the past several years, SaaS (software as a service) has become an attractive option for companies looking to save money and simplify their computing infrastructures. SaaS is an interesting group of techniques for moving computing from the desktop to the cloud; however, as it grows in popularity, engineers should be aware of some of the fundamental limitations they face when developing these kinds of distributed applications - in particular, the finite speed of light.

Fighting Spam with Reputation Systems:
User-submitted spam fingerprints

Spam is everywhere, clogging the inboxes of e-mail users worldwide. Not only is it an annoyance, it erodes the productivity gains afforded by the advent of information technology. Workers plowing through hours of legitimate e-mail every day also must contend with removing a significant amount of illegitimate e-mail. Automated spam filters have dramatically reduced the amount of spam seen by the end users who employ them, but the amount of training required rivals the amount of time needed simply to delete the spam without the assistance of a filter.

Finding More Than One Worm in the Apple:
If you see something, say something.

In February Apple revealed and fixed an SSL (Secure Sockets Layer) vulnerability that had gone undiscovered since the release of iOS 6.0 in September 2012. It left users vulnerable to man-in-the-middle attacks thanks to a short circuit in the SSL/TLS (Transport Layer Security) handshake algorithm introduced by the duplication of a goto statement. Since the discovery of this very serious bug, many people have written about potential causes.

Finding Usability Bugs with Automated Tests:
Automated usability tests can be valuable companions to in-person tests.

Ideally, all software should be easy to use and accessible for a wide range of people; however, even software that appears to be modern and intuitive often falls short of the most basic usability and accessibility goals. Why does this happen? One reason is that sometimes our designs look appealing so we skip the step of testing their usability and accessibility; all in the interest of speed, reducing costs, and competitive advantage.

Flash Disk Opportunity for Server Applications:
Future flash-based disks could provide breakthroughs in IOPS, power, reliability, and volumetric capacity when compared with conventional disks.

NAND flash densities have been doubling each year since 1996. Samsung announced that its 32-gigabit NAND flash chips would be available in 2007. This is consistent with Chang-gyu Hwang’s flash memory growth model1 that NAND flash densities will double each year until 2010. Hwang recently extended that 2003 prediction to 2012, suggesting 64 times the current density250 GB per chip. This is hard to credit, but Hwang and Samsung have delivered 16 times since his 2003 article when 2-GB chips were just emerging. So, we should be prepared for the day when a flash drive is a terabyte(!) .

Flash Storage Today:
Can flash memory become the foundation for a new tier in the storage hierarchy?

The past few years have been an exciting time for flash memory. The cost has fallen dramatically as fabrication has become more efficient and the market has grown; the density has improved with the advent of better processes and additional bits per cell; and flash has been adopted in a wide array of applications. The flash ecosystem has expanded and continues to expand especially for thumb drives, cameras, ruggedized laptops, and phones in the consumer space.

Four Billion Little Brothers? Privacy, mobile phones, and ubiquitous data collection:
Participatory sensing technologies could improve our lives and our communities, but at what cost to our privacy?

They place calls, surf the Internet, and there are close to 4 billion of them in the world. Their built-in microphones, cameras, and location awareness can collect images, sound, and GPS data. Beyond chatting and texting, these features could make phones ubiquitous, familiar tools for quantifying personal patterns and habits. They could also be platforms for thousands to document a neighborhood, gather evidence to make a case, or study mobility and health. This data could help you understand your daily carbon footprint, exposure to air pollution, exercise habits, and frequency of interactions with family and friends.

From COM to Common:
Component software’s 10-year journey toward ubiquity

Ten years ago, the term component software meant something relatively specific and concrete. A small number of software component frameworks more or less defined the concept for most people. Today, few terms in the software industry are less precise than component software. There are now many different forms of software componentry for many different purposes. The technologies and methodologies of 10 years ago have evolved in fundamental ways and have been joined by an explosion of new technologies and approaches that have redefined our previously held notions of component software.

From IR to Search, and Beyond:
Searching has come a long way since the 60s, but have we only just begun?

It’s been nearly 60 years since Vannevar Bush’s seminal article, ’As We May Think,’ portrayed the image of a scholar aided by a machine, “a device in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility.”

From Liability to Advantage: A Conversation with John Graham-Cumming and John Ousterhout:
Software production has become a bottleneck in many development organizations.

Software production (the back-end of software development, including tasks such as build, test, package and deploy) has become a bottleneck in many development organizations. In this interview Electric Cloud founder John Ousterhout explains how you can turn software production from a liability to a competitive advantage.

From Server Room to Living Room:
How open source and TiVo became a perfect match

The open source movement, exemplified by the growing acceptance of Linux, is finding its way not only into corporate environments but also into a home near you. For some time now, high-end applications such as software development, computer-aided design and manufacturing, and heavy computational applications have been implemented using Linux and generic PC hardware.

From the EDVAC to WEBVACs:
Cloud computing for computer scientists

By now everyone has heard of cloud computing and realized that it is changing how both traditional enterprise IT and emerging startups are building solutions for the future. Is this trend toward the cloud just a shift in the complicated economics of the hardware and software industry, or is it a fundamentally different way of thinking about computing? Having worked in the industry, I can confidently say it is both.

Fun and Games: Multi-Language Development:
Game development can teach us much about the common practice of combining multiple languages in a single project.

Computer games (or "electronic games" if you encompass those games played on console-class hardware) comprise one of the fastest-growing application markets in the world. Within the development community that creates these entertaining marvels, multi-language development is becoming more commonplace as games become more and more complex. Today, asking a development team to construct a database-enabled Web site with the requirement that it be written entirely in C++ would earn scornful looks and rolled eyes, but not long ago the idea that multiple languages were needed to accomplish a given task was scoffed at.

Functional at Scale:
Applying functional programming principles to distributed computing projects

Modern server software is demanding to develop and operate: it must be available at all times and in all locations; it must reply within milliseconds to user requests; it must respond quickly to capacity demands; it must process a lot of data and even more traffic; it must adapt quickly to changing product needs; and in many cases it must accommodate a large engineering organization, its many engineers the proverbial cooks in a big, messy kitchen.

Future Graphics Architectures:
GPUs continue to evolve rapidly, but toward what?

Graphics architectures are in the midst of a major transition. In the past, these were specialized architectures designed to support a single rendering algorithm: the standard Z buffer. Realtime 3D graphics has now advanced to the point where the Z-buffer algorithm has serious shortcomings for generating the next generation of higher-quality visual effects demanded by games and other interactive 3D applications. There is also a desire to use the high computational capability of graphics architectures to support collision detection, approximate physics simulations, scene management, and simple artificial intelligence.

Fuzzy Boundaries: Objects, Components, and Web Services:
It’s easy to transform objects into components and Web services, but how do we know which is right for the job?

If you are an object-oriented programmer, you will understand the code snippet, even if you are not familiar with the language (C#, not that it matters). You will not be surprised to learn that this program will print out the following line to the console: woof.

GPUs: A Closer Look:
As the line between GPUs and CPUs begins to blur, it’s important to understand what makes GPUs tick.

A gamer wanders through a virtual world rendered in near- cinematic detail. Seconds later, the screen fills with a 3D explosion, the result of unseen enemies hiding in physically accurate shadows. Disappointed, the user exits the game and returns to a computer desktop that exhibits the stylish 3D look-and-feel of a modern window manager. Both of these visual experiences require hundreds of gigaflops of computing performance, a demand met by the GPU (graphics processing unit) present in every consumer PC.

Game Development: Harder Than You Think:
Ten or twenty years ago it was all fun and games. Now it’s blood, sweat, and code.

The hardest part of making a game has always been the engineering. In times past, game engineering was mainly about low-level optimization—writing code that would run quickly on the target computer, leveraging clever little tricks whenever possible. But in the past ten years, games have ballooned in complexity. Now the primary technical challenge is simply getting the code to work to produce an end result that bears some semblance to the desired functionality. To the extent that we optimize, we are usually concerned with high-level algorithmic choices.

Gaming Graphics: The Road to Revolution:
From laggard to leader, game graphics are taking us in new directions.

It has been a long journey from the days of multicolored sprites on tiled block backgrounds to the immersive 3D environments of modern games. What used to be a job for a single game creator is now a multifaceted production involving staff from every creative discipline. The next generation of console and home computer hardware is going to bring a revolutionary leap in available computing power; a teraflop (trillion floating-point operations per second) or more will be on tap from commodity hardware.

Garbage Collection as a Joint Venture:
A collaborative approach to reclaiming memory in heterogeneous software systems

Cross-component tracing is a way to solve the problem of reference cycles across component boundaries. This problem appears as soon as components can form arbitrary object graphs with nontrivial ownership across API boundaries. An incremental version of CCT is implemented in V8 and Blink, enabling effective and efficient reclamation of memory in a safe manner.

Getting Bigger Reach Through Speech:
Developers have a chance to significantly expand the appeal and reach of their applications by voice-enabling their applications, but is that going to be enough?

Mark Ericson, vice president of product strategy for BlueNote Networks argues that in order to take advantage of new voice technologies you have to have a plan for integrating that capability directly into the applications that drive your existing business processes.

Getting Gigascale Chips:
Challenges and Opportunities in Continuing Moore’s Law

Processor performance has increased by five orders of magnitude in the last three decades, made possible by following Moore’s law - that is, continued technology scaling, improved transistor performance to increase frequency, additional (to avoid repetition) integration capacity to realize complex architectures, and reduced energy consumed per logic operation to keep power dissipation within limits. Advances in software technology, such as rich multimedia applications and runtime systems, exploited this performance explosion, delivering to end users higher productivity, seamless Internet connectivity, and even multimedia and entertainment.

Getting What You Measure:
Four common pitfalls in using software metrics for project management

Software metrics - helpful tools or a waste of time? For every developer who treasures these mathematical abstractions of software systems there is a developer who thinks software metrics are invented just to keep project managers busy. Software metrics can be very powerful tools that help achieve your goals but it is important to use them correctly, as they also have the power to demotivate project teams and steer development in the wrong direction.

Go Static or Go Home:
In the end, dynamic systems are simply less secure.

Most current and historic problems in computer and network security boil down to a single observation: letting other people control our devices is bad for us. At another time, I’ll explain what I mean by "other people" and "bad." For the purpose of this article, I’ll focus entirely on what I mean by control. One way we lose control of our devices is to external distributed denial of service (DDoS) attacks, which fill a network with unwanted traffic, leaving no room for real ("wanted") traffic. Other forms of DDoS are similar: an attack by the Low Orbit Ion Cannon (LOIC), for example, might not totally fill up a network, but it can keep a web server so busy answering useless attack requests that the server can’t answer any useful customer requests.

Going with the Flow:
Workflow systems can provide value beyond automating business processes.

An organization consists of two worlds. The real world contains the organization’s structure, physical goods, employees, and other organizations. The virtual world contains the organization’s computerized infrastructure, including its applications and databases. Workflow systems bridge the gap between these two worlds. They provide both a model of the organization’s design and a runtime to execute the model.

Hack for Hire:
Investigating the emerging black market of retail email account hacking services

Hack-for-hire services charging $100-$400 per contract were found to produce sophisticated, persistent, and personalized attacks that were able to bypass 2FA via phishing. The demand for these services, however, appears to be limited to a niche market, as evidenced by the small number of discoverable services, an even smaller number of successful services, and the fact that these attackers target only about one in a million Google users.

Hadoop Superlinear Scalability:
The perpetual motion of parallel performance

We often see more than 100 percent speedup efficiency! came the rejoinder to the innocent reminder that you can’t have more than 100 percent of anything. But this was just the first volley from software engineers during a presentation on how to quantify computer system scalability in terms of the speedup metric. In different venues, on subsequent occasions, that retort seemed to grow into a veritable chorus that not only was superlinear speedup commonly observed, but also the model used to quantify scalability for the past 20 years failed when applied to superlinear speedup data.

Hard Disk Drives: The Good, the Bad and the Ugly!:
HDDs are like the bread in a peanut butter and jelly sandwich.

HDDs are like the bread in a peanut butter and jelly sandwich—sort of an unexciting piece of hardware necessary to hold the “software.” They are simply a means to an end. HDD reliability, however, has always been a significant weak link, perhaps the weak link, in data storage. In the late 1980s people recognized that HDD reliability was inadequate for large data storage systems so redundancy was added at the system level with some brilliant software algorithms, and RAID (redundant array of inexpensive disks) became a reality. RAID moved the reliability requirements from the HDD itself to the system of data disks.

Hazy: Making it Easier to Build and Maintain Big-data Analytics:
Racing to unleash the full potential of big data with the latest statistical and machine-learning techniques.

The rise of big data presents both big opportunities and big challenges in domains ranging from enterprises to sciences. The opportunities include better-informed business decisions, more efficient supply-chain management and resource allocation, more effective targeting of products and advertisements, better ways to "organize the world’s information," faster turnaround of scientific discoveries, etc.

Heterogeneous Computing: Here to Stay:
Hardware and Software Perspectives

Mentions of the buzzword heterogeneous computing have been on the rise in the past few years and will continue to be heard for years to come, because heterogeneous computing is here to stay. What is heterogeneous computing, and why is it becoming the norm? How do we deal with it, from both the software side and the hardware side? This article provides answers to some of these questions and presents different points of view on others.

Hidden in Plain Sight:
Improvements in the observability of software can help you diagnose your most crippling performance problems.

In December 1997, Sun Microsystems had just announced its new flagship machine: a 64-processor symmetric multiprocessor supporting up to 64 gigabytes of memory and thousands of I/O devices. As with any new machine launch, Sun was working feverishly on benchmarks to prove the machine’s performance. While the benchmarks were generally impressive, there was one in particular that was exhibiting unexpectedly low performance. The benchmark machine would occasionally become mysteriously distracted: Benchmark activity would practically cease, but the operating system kernel remained furiously busy. After some number of minutes spent on unknown work, the operating system would suddenly right itself: Benchmark activity would resume at full throttle and run to completion.

High Performance Web Sites:
Want to make your Web site fly? Focus on front-end performance.

Google Maps, Yahoo! Mail, Facebook, MySpace, YouTube, and Amazon are examples of Web sites built to scale. They access petabytes of data sending terabits per second to millions of users worldwide. The magnitude is awe-inspiring. Users view these large-scale Web sites from a narrower perspective. The typical user has megabytes of data that are downloaded at a few hundred kilobits per second. Users are not so interested in the massive number of requests per second being served; they care more about their individual requests.

How Do I Model State? Let Me Count the Ways:
A study of the technology and sociology of Web services specifications

There is nothing like a disagreement concerning an arcane technical matter to bring out the best (and worst) in software architects and developers. As every reader knows from experience, it can be hard to get to the bottom of what exactly is being debated. One reason for this lack of clarity is often that different people care about different aspects of the problem. In the absence of agreement concerning the problem, it can be difficult to reach an agreement about the solutions.

How Fast is Your Web Site?:
Web site performance data has never been more readily available.

The overwhelming evidence indicates that a Web site’s performance (speed) correlates directly to its success, across industries and business metrics. With such a clear correlation (and even proven causation), it is important to monitor how your Web site performs. So, how fast is your Web site?

How Not to Write Fortran in Any Language:
There are characteristics of good coding that transcend all programming languages.

There’s no obfuscated Perl contest because it’s pointless.

How OSGi Changed My Life:
The promises of the Lego hypothesis have yet to materialize fully, but they remain a goal worth pursuing.

In the early 1980s I discovered OOP (object-oriented programming) and fell in love with it, head over heels. As usual, this kind of love meant convincing management to invest in this new technology, and most important of all, send me to cool conferences. So I pitched the technology to my manager. I sketched him the rosy future, how one day we would create applications from ready-made classes. We would get those classes from a repository, put them together, and voila, a new application would be born. Today we take objects more or less for granted, but if I am honest, the pitch I gave to my manager in 1985 never really materialized.

How Will Astronomy Archives Survive the Data Tsunami?:
Astronomers are collecting more data than ever. What practices can keep them ahead of the flood?

Astronomy is already awash with data: currently 1 PB of public data is electronically accessible, and this volume is growing at 0.5 PB per year. The availability of this data has already transformed research in astronomy, and the STScI now reports that more papers are published with archived data sets than with newly acquired data. This growth in data size and anticipated usage will accelerate in the coming few years as new projects such as the LSST, ALMA, and SKA move into operation. These new projects will use much larger arrays of telescopes and detectors or much higher data acquisition rates than are now used.

How to De-identify Your Data:
Balancing statistical accuracy and subject privacy in large social-science data sets

Big data is all the rage; using large data sets promises to give us new insights into questions that have been difficult or impossible to answer in the past. This is especially true in fields such as medicine and the social sciences, where large amounts of data can be gathered and mined to find insightful relationships among variables. Data in such fields involves humans, however, and thus raises issues of privacy that are not faced by fields such as physics or astronomy.

How to Live in a Post-Meltdown and -Spectre World:
Learn from the past to prepare for the next battle.

Spectre and Meltdown create a risk landscape that has more questions than answers. This article addresses how these vulnerabilities were triaged when they were announced and the practical defenses that are available. Ultimately, these vulnerabilities present a unique set of circumstances, but for the vulnerability management program at Goldman Sachs, the response was just another day at the office.

Human-Centered Approach to Static-Analysis-Driven Developer Tools:
The future depends on good HCI

Complex and opaque systems do not scale easily. A human-centered approach for evolving tools and practices is essential to ensuring that software is scaled safely and securely. Static analysis can unveil information about program behavior, but the goal of deriving this information should not be to accumulate hairsplitting detail. HCI can help direct static-analysis techniques into developer-facing systems that structure information and embody relationships in representations that closely mirror a programmer's thought. The survival of great software depends on programming languages that support, rather than inhibit, communicating, reasoning, and abstract thinking.

I/O Virtualization:
Decoupling a logical device from its physical implementation offers many compelling advantages.

The term virtual is heavily overloaded, evoking everything from virtual machines running in the cloud to avatars running across virtual worlds. Even within the narrowfigureer context of computer I/O, virtualization has a long, diverse history, exemplified by logical devices that are deliberately separate from their physical instantiations.

Idempotence Is Not a Medical Condition:
An essential property for reliable systems

The definition of distributed computing can be confusing. Sometimes, it refers to a tightly coupled cluster of computers working together to look like one larger computer. More often, however, it refers to a bunch of loosely related applications chattering together without a lot of system-level support. This lack of support in distributed computing environments makes it difficult to write applications that work together. Messages sent between systems do not have crisp guarantees for delivery. They can get lost, and so, after a timeout, they are retried. The application on the other side of the communication may see multiple messages arrive where one was intended.

Identity by Any Other Name:
The complex cacophony of intertwined systems

New emerging systems and protocols both tighten and loosen our notions of identity, and that’s good! They make it easier to get stuff done. REST, IoT, big data, and machine learning all revolve around notions of identity that are deliberately kept flexible and sometimes ambiguous. Notions of identity underlie our basic mechanisms of distributed systems, including interchangeability, idempotence, and immutability.

Idle-Time Garbage-Collection Scheduling:
Taking advantage of idleness to reduce dropped frames and memory consumption

Google’s Chrome web browser strives to deliver a smooth user experience. An animation will update the screen at 60 FPS (frames per second), giving Chrome around 16.6 milliseconds to perform the update. Within these 16.6 ms, all input events have to be processed, all animations have to be performed, and finally the frame has to be rendered. A missed deadline will result in dropped frames. These are visible to the user and degrade the user experience. Such sporadic animation artifacts are referred to here as jank. This article describes an approach implemented in the JavaScript engine V8, used by Chrome, to schedule garbage-collection pauses during times when Chrome is idle.

If You Have Too Much Data, then "Good Enough" Is Good Enough:
In today’s humongous database systems, clarity may be relaxed, but business needs can still be met.

Classic database systems offer crisp answers for a relatively small amount of data. These systems hold their data in one or a relatively small number of computers. With a tightly defined schema and transactional consistency, the results returned from queries are crisp and accurate. New systems have humongous amounts of data content, change rates, and querying rates and take lots of computers to hold and process. The data quality and meaning are fuzzy. The schema, if present, is likely to vary across the data. The origin of the data may be suspect, and its staleness may vary.

Immutability Changes Everything:
We need it, we can afford it, and the time is now.

There is an inexorable trend toward storing and sending immutable data. We need immutability to coordinate at a distance, and we can afford immutability as storage gets cheaper. This article is an amuse-bouche sampling the repeated patterns of computing that leverage immutability. Climbing up and down the compute stack really does yield a sense of déjà vu all over again.

Improving Performance on the Internet:
Given the Internet’s bottlenecks, how can we build fast, scalable content-delivery systems?

When it comes to achieving performance, reliability, and scalability for commercial-grade Web applications, where is the biggest bottleneck? In many cases today, we see that the limiting bottleneck is the middle mile, or the time data spends traveling back and forth across the Internet, between origin server and end user.

Industrial Scale Agile - from Craft to Engineering:
Essence is instrumental in moving software development toward a true engineering discipline.

There are many, many ways to illustrate how fragile IT investments can be. You just have to look at the way that, even after huge investments in education and coaching, many organizations are struggling to broaden their agile adoption to the whole of their organization - or at the way other organizations are struggling to maintain the momentum of their agile adoptions as their teams change and their systems mature.

Industry-scale Knowledge Graphs: Lessons and Challenges:
Five diverse technology companies show how it’s done

This article looks at the knowledge graphs of five diverse tech companies, comparing the similarities and differences in their respective experiences of building and using the graphs, and discussing the challenges that all knowledge-driven enterprises face today. The collection of knowledge graphs discussed here covers the breadth of applications, from search, to product descriptions, to social networks.

Information Extraction:
Distilling structured data from unstructured text

In 2001 the U.S. Department of Labor was tasked with building a Web site that would help people find continuing education opportunities at community colleges, universities, and organizations across the country. The department wanted its Web site to support fielded Boolean searches over locations, dates, times, prerequisites, instructors, topic areas, and course descriptions. Ultimately it was also interested in mining its new database for patterns and educational trends. This was a major data-integration project, aiming to automatically gather detailed, structured information from tens of thousands of individual institutions every three months.

Injecting Errors for Fun and Profit:
Error-detection and correction features are only as good as our ability to test them.

It is an unfortunate fact of life that anything with moving parts eventually wears out and malfunctions, and electronic circuitry is no exception. In this case, of course, the moving parts are electrons. In addition to the wear-out mechanisms of electromigration (the moving electrons gradually push the metal atoms out of position, causing wires to thin, thus increasing their resistance and eventually producing open circuits) and dendritic growth (the voltage difference between adjacent wires causes the displaced metal atoms to migrate toward each other, just as magnets will attract each other, eventually causing shorts), electronic circuits are also vulnerable to background radiation.

Instant Messaging or Instant Headache?:
IM has found a home within the enterprise, but it’s far from secure.

It’s a reality. You have IM (instant messaging) clients in your environment. You have already recognized that it is eating up more and more of your network bandwidth and with Microsoft building IM capability into its XP operating system and applications, you know this will only get worse. Management is also voicing concerns over the lost user productivity caused by personal conversations over this medium. You have tried blocking these conduits for conversation, but it is a constant battle.

Integrating RFID:
Data management and inventory control are about to get a whole lot more interesting.

RFID (radio frequency identification) has received a great deal of attention in the commercial world over the past couple of years. The excitement stems from a confluence of events. First, through the efforts of the former Auto-ID Center and its sponsor companies, the prospects of low-cost RFID tags and a networked supply chain have come within reach of a number of companies. Second, several commercial companies and government bodies, such as Wal-Mart and Target in the United States, Tesco in Europe, and the U.S. Department of Defense, have announced RFID initiatives in response to technology improvements.

Intellectual Property and Software Piracy:
The Power of IP Protection and Software Licensing, an interview with Aladdin vice president Gregg Gronowski

We’re here today to talk about intellectual property and the whole issue of software piracy and our friends at Aladdin are considered one of the de facto standards today for protecting software IP, preventing software piracy, and enabling software licensing and compliance. So joining us today to discuss that topic is Aladdin Vice President, Greg Gronowski.

Interactive Dynamics for Visual Analysis:
A taxonomy of tools that support the fluent and flexible use of visualizations

The increasing scale and availability of digital data provides an extraordinary resource for informing public policy, scientific discovery, business strategy, and even our personal lives. To get the most out of such data, however, users must be able to make sense of it: to pursue questions, uncover patterns of interest, and identify (and potentially correct) errors. In concert with data-management systems and statistical algorithms, analysis requires contextualized human judgments regarding the domain-specific significance of the clusters, trends, and outliers discovered in data.

Intermediate Representation:
The increasing significance of intermediate representations in compilers

Program compilation is a complicated process. A compiler is a software program that translates a high-level source language program into a form ready to execute on a computer. Early in the evolution of compilers, designers introduced IRs (intermediate representations, also commonly called intermediate languages) to manage the complexity of the compilation process. The use of an IR as the compiler’s internal representation of the program enables the compiler to be broken up into multiple phases and components, thus benefiting from modularity.

Internal Access Controls:
Trust, but Verify

Every day seems to bring news of another dramatic and high-profile security incident, whether it is the discovery of longstanding vulnerabilities in widely used software such as OpenSSL or Bash, or celebrity photographs stolen and publicized. There seems to be an infinite supply of zero-day vulnerabilities and powerful state-sponsored attackers. In the face of such threats, is it even worth trying to protect your systems and data? What can systems security designers and administrators do?

Is Open Source Right for You?:
A fictional case study of open source in a commercial software shop

The media often present open source software as a direct competitor to commercial software. This depiction, usually pitting David (Linux) against Goliath (Microsoft), makes for fun reading in the weekend paper. However, it mostly misses the point of what open source means to a development organization. In this article, I use the experiences of GizmoSoft (a fictitious software company) to present some perspectives on the impact of open source software usage in a software development shop.

Is Persistent Memory Persistent?:
A simple and inexpensive test of failure-atomic update mechanisms

Power failures pose the most severe threat to application data integrity, and painful experience teaches that the integrity promises of failure-atomic update mechanisms can’t be taken at face value. Diligent developers and operators insist on confirming integrity claims by extensive firsthand tests. This article presents a simple and inexpensive testbed capable of subjecting storage devices, system software, and application software to ten thousand sudden whole-system power-interruption tests per week.

Is There a Single Method for the Internet of Things?:
Essence can keep software development for the IoT from becoming unwieldy.

The Industrial Internet Consortium predicts the IoT (Internet of Things) will become the third technological revolution after the Industrial Revolution and the Internet Revolution. Its impact across all industries and businesses can hardly be imagined. Existing software (business, telecom, aerospace, defense, etc.) is expected to be modified or redesigned, and a huge amount of new software, solving new problems, will have to be developed. As a consequence, the software industry should welcome new and better methods.

It Probably Works:
Probabilistic algorithms are all around us--not only are they acceptable, but some programmers actually seek out chances to use them.

Probabilistic algorithms exist to solve problems that are either impossible or unrealistic (too expensive, too time-consuming, etc.) to solve precisely. In an ideal world, you would never actually need to use probabilistic algorithms. To programmers who are not familiar with them, the idea can be positively nervewracking: "How do I know that it will actually work? What if it’s inexplicably wrong? How can I debug it? Maybe we should just punt on this problem, or buy a whole lot more servers..."

Java Security Architecture Revisited:
Hard technical problems and tough business challenges

This article looks back at a few of the hardest technical problems from a design and engineering perspective, as well as some tough business challenges for which research scientists are rarely trained. Li Gong offers a retrospective here culled from four previous occasions when he had the opportunity to dig into old notes and refresh his memory.

Java in a Teacup:
Programming Bluetooth-enabled devices using J2ME

Few technology sectors evolve as fast as the wireless industry. As the market and devices mature, the need (and potential) for mobile applications grows. More and more mobile devices are delivered with the Java platform installed, enabling a large base of Java programmers to try their hand at embedded programming. Unfortunately, not all Java mobile devices are created equal, presenting many challenges to the new J2ME (Java 2 Platform, Micro Edition) programmer. Using a sample game application, this article illustrates some of the challenges associated with J2ME and Bluetooth programming.

JavaScript and the Netflix User Interface:
Conditional dependency resolution

In the two decades since its introduction, JavaScript has become the de facto official language of the Web. JavaScript trumps every other language when it comes to the number of runtime environments in the wild. Nearly every consumer hardware device on the market today supports the language in some way. While this is done most commonly through the integration of a Web browser application, many devices now also support Web views natively as part of the operating system UI (user interface).

Keeping Bits Safe: How Hard Can It Be?:
As storage systems grow larger and larger, protecting their data for long-term storage is becoming more and more challenging.

These days, we are all data pack rats. Storage is cheap, so if there’s a chance the data could possibly be useful, we keep it. We know that storage isn’t completely reliable, so we keep backup copies as well. But the more data we keep, and the longer we keep it, the greater the chance that some of it will be unrecoverable when we need it.

Keeping Score in the IT Compliance Game:
ALM can help organizations meet tough IT compliance requirements.

Achieving developer acceptance of standardized procedures for managing applications from development to release is one of the largest hurdles facing organizations today. Establishing a standardized development-to-release workflow, often referred to as the ALM (application lifecycle management) process, is particularly critical for organizations in their efforts to meet tough IT compliance mandates. This is much easier said than done, as different development teams have created their own unique procedures that are undocumented, unclear, and nontraceable.

Lack of Priority Queuing Considered Harmful:
We’re in sore need of critical Internet infrastructure protection.

Most modern routers consist of several line cards that perform packet lookup and forwarding, all controlled by a control plane that acts as the brain of the router, performing essential tasks such as management functions, error reporting, control functions including route calculations, and adjacency maintenance. This control plane has many names; in this article it is the route processor, or RP. The route processor calculates the forwarding table and downloads it to the line cards using a control-plane bus. The line cards perform the actual packet lookup and forwarding.

Languages, Levels, Libraries, and Longevity:
New programming languages are born every day. Why do some succeed and some fail?

In 50 years, we’ve already seen numerous programming systems come and (mostly) go, although some have remained a long time and will probably do so for: decades? centuries? millennia? The questions about language designs, levels of abstraction, libraries, and resulting longevity are numerous. Why do new languages arise? Why is it sometimes easier to write new software than to adapt old software that works? How many different levels of languages make sense? Why do some languages last in the face of “better” ones?

Leaking Space:
Eliminating memory hogs

A space leak occurs when a computer program uses more memory than necessary. In contrast to memory leaks, where the leaked memory is never released, the memory consumed by a space leak is released, but later than expected. This article presents example space leaks and how to spot and eliminate them.

Learning from the Web:
The Web has taught us many lessons about distributed computing, but some of the most important ones have yet to fully take hold.

In the past decade we have seen a revolution in computing that transcends anything seen to date in terms of scope and reach, but also in terms of how we think about what makes up “good” and “bad” computing.

Lessons from the Floor:
The manufacturing industry can teach us a lot about measuring performance in large-scale Internet services.

The January monthly service quality meeting started normally. Around the table were representatives from development, operations, marketing, and product management, and the agenda focused on the prior month’s performance. As usual, customer-impacting incidents and quality of service were key topics, and I was armed with the numbers showing the average uptime for the part of the service that I represent: MSN, the Microsoft family of services that includes e-mail, Instant Messenger, news, weather and sports, etc.

Lessons from the Letter:
Security flaws in a large organization

I recently received a letter in which a company notified me that they had exposed some of my personal information. While it is now quite common for personal data to be stolen, this letter amazed me because of how well it pointed out two major flaws in the systems of the company that lost the data. I am going to insert three illuminating paragraphs here and then discuss what they actually can teach us.

Leveraging Application Frameworks:
Why frameworks are important and how to apply them effectively

In today’s competitive, fast-paced computing industry, successful software must increasingly be: (1) extensible to support successions of quick updates and additions to address new requirements and take advantage of emerging markets; (2) flexible to support a growing range of multimedia data types, traffic flows, and end-to-end QoS (quality of service) requirements; (3) portable to reduce the effort required to support applications on heterogeneous operating-system platforms and compilers; (4) reliable to ensure that applications are robust and tolerant to faults; (5) scalable to enable applications to handle larger numbers of clients simultaneously; and (6) affordable to ensure that the total ownership costs of software acquisition and evolution are not prohibitively high.

Life Beyond Distributed Transactions:
An apostate’s opinion

This article explores and names some of the practical approaches used in the implementation of large-scale mission-critical applications in a world that rejects distributed transactions. Topics include the management of fine-grained pieces of application data that may be repartitioned over time as the application grows. Design patterns support sending messages between these repartitionable pieces of data.

META II: Digital Vellum in the Digital Scriptorium:
Revisiting Schorre’s 1962 compiler-compiler

Some people do living history -- reviving older skills and material culture by reenacting Waterloo or knapping flint knives. One pleasant rainy weekend in 2012, I set my sights a little more recently and settled in for a little meditative retro-computing, ca. 1962, following the ancient mode of transmission of knowledge: lecture and recitation -- or rather, grace of living in historical times, lecture (here, in the French sense, reading) and transcription (or even more specifically, grace of living post-Post, lecture and reimplementation).

Major-league SEMAT: Why Should an Executive Care?:
Becoming better, faster, cheaper, and happier

In today’s ever more competitive world, boards of directors and executives demand that CIOs and their teams deliver "more with less." Studies show, without any real surprise, that there is no one-size-fits-all method to suit all software initiatives, and that a practice-based approach with some light but effective degree of order and governance is the goal of most software-development departments.

Making Money Using Math:
Modern applications are increasingly using probabilistic machine-learned models.

A big difference between human-written code and learned models is that the latter are usually not represented by text and hence are not understandable by human developers or manipulable by existing tools. The consequence is that none of the traditional software engineering techniques for conventional programs (such as code reviews, source control, and debugging) are applicable anymore. Since incomprehensibility is not unique to learned code, these aspects are not of concern here.

Making SIP Make Cents:
P2P payments using SIP could enable new classes of micropayment applications and business models.

The Session Initiation Protocol (SIP) is used to set up realtime sessions in IP-based networks. These sessions might be for audio, video, or IM communications, or they might be used to relay presence information. SIP service providers are mainly focused on providing a service that copies that provided by the PSTN (public switched telephone network) or the PLMN (public land mobile network) to the Internet-based environment.

Making Sense of Revision-control Systems:
Whether distributed or centralized, all revision-control systems come with complicated sets of tradeoffs. How do you find the best match between tool and team?

Modern software is tremendously complicated, and the methods that teams use to manage its development reflect this complexity. Though many organizations use revision-control software to track and manage the complexity of a project as it evolves, the topic of how to make an informed choice of revision-control tools has received scant attention. Until fairly recently, the world of revision control was moribund, so there was simply not much to say on this subject.

Making a Case for Efficient Supercomputing:
It is time for the computing community to use alternative metrics for evaluating performance.

A supercomputer evokes images of “big iron“ and speed; it is the Formula 1 racecar of computing. As we venture forth into the new millennium, however, I argue that efficiency, reliability, and availability will become the dominant issues by the end of this decade, not only for supercomputing, but also for computing in general.

Making the Mobile Web Faster:
Mobile performance issues? Fix the back end, not just the client.

Mobile clients have been on the rise and will only continue to grow. This means that if you are serving clients over the Internet, you cannot ignore the customer experience on a mobile device. There are many informative articles on mobile performance, and just as many on general API design, but you’ll find few discussing the design considerations needed to optimize the back-end systems for mobile clients. Whether you have an app, mobile Web site, or both, it is likely that these clients are consuming APIs from your back-end systems.

Making the Web Faster with HTTP 2.0:
HTTP continues to evolve

HTTP (Hypertext Transfer Protocol) is one of the most widely used application protocols on the Internet. Since its publication, RFC 2616 (HTTP 1.1) has served as a foundation for the unprecedented growth of the Internet: billions of devices of all shapes and sizes, from desktop computers to the tiny Web devices in our pockets, speak HTTP every day to deliver news, video, and millions of other Web applications we have all come to depend on in our everyday lives.

Managing Collaboration:
Jeff Johnstone of TechExcel explains why there is a need for a new approach to application lifecycle management that better reflects the business requirements and challenges facing development teams.

I think that fundamentally development is thought of, has become more of a business process than simply a set of tools. In the past, like you said, developers and development organizations were kind of on their own. They were fairly autonomous and they would do things that were appropriate for each piece of the process and they would adopt technologies that were appropriate at a technology and tool level, but they didn’t really think of themselves as an integral part of any higher business process.

Managing Contention for Shared Resources on Multicore Processors:
Contention for caches, memory controllers, and interconnects can be alleviated by contention-aware scheduling algorithms.

Modern multicore systems are designed to allow clusters of cores to share various hardware structures, such as LLCs (last-level caches; for example, L2 or L3), memory controllers, and interconnects, as well as prefetching hardware. We refer to these resource-sharing clusters as memory domains, because the shared resources mostly have to do with the memory hierarchy.

Managing Semi-Structured Data:
I vividly remember during my first college class my fascination with the relational database.

In that class I learned how to build a schema for my information, and I learned that to obtain an accurate schema there must be a priori knowledge of the structure and properties of the information to be modeled. I also learned the ER (entity-relationship) model as a basic tool for all further data modeling, as well as the need for an a priori agreement on both the general structure of the information and the vocabularies used by all communities producing, processing, or consuming this information.

Managing Technical Debt:
Shortcuts that save money and time today can cost you down the road.

In 1992, Ward Cunningham published a report at OOPSLA (Object-oriented Programming, Systems, Languages, and Applications) in which he proposed the concept of technical debt. He defines it in terms of immature code: "Shipping first-time code is like going into debt." Technical debt isn’t limited to first-time code, however. There are many ways and reasons (not all bad) to take on technical debt.

Managing the Hidden Costs of Coordination:
Controlling coordination costs when multiple, distributed perspectives are essential

Some initial considerations to control cognitive costs for incident responders include: (1) assessing coordination strategies relative to the cognitive demands of the incident; (2) recognizing when adaptations represent a tension between multiple competing demands (coordination and cognitive work) and seeking to understand them better rather than unilaterally eliminating them; (3) widening the lens to study the joint cognition system (integration of human-machine capabilities) as the unit of analysis; and (4) viewing joint activity as an opportunity for enabling reciprocity across inter- and intra-organizational boundaries.

Massively Multiplayer Middleware:
Building scaleable middleware for ultra-massive online games teaches a lesson we all can use: Big project, simple design.

Wish is a multiplayer, online, fantasy role-playing game being developed by Mutable Realms. It differs from similar online games in that it allows tens of thousands of players to participate in a single game world. Allowing such a large number of players requires distributing the processing load over a number of machines and raises the problem of choosing an appropriate distribution technology.

Maximizing Power Efficiency with Asymmetric Multicore Systems:
Asymmetric multicore systems promise to use a lot less energy than conventional symmetric processors. How can we develop software that makes the most out of this potential?

In computing systems, a CPU is usually one of the largest consumers of energy. For this reason, reducing CPU power consumption has been a hot topic in the past few years in both the academic community and the industry. In the quest to create more power-efficient CPUs, several researchers have proposed an asymmetric multicore architecture that promises to save a significant amount of power while delivering similar performance to conventional symmetric multicore processors.

Meet the Virts:
Virtualization technology isn’t new, but it has matured a lot over the past 30 years.

When you dig into the details of supposedly overnight success stories, you frequently discover that they’ve actually been years in the making. Virtualization has been around for more than 30 years since the days when some of you were feeding stacks of punch cards into very physical machines yet in 2007 it tipped. VMware was the IPO sensation of the year; in November 2007 no fewer than four major operating system vendors (Microsoft, Oracle, Red Hat, and Sun) announced significant new virtualization capabilities; and among fashionable technologists it seems virtual has become the new black.

Metamorphosis: the Coming Transformation of Translational Systems Biology:
In the future computers will mine patient data to deliver faster, cheaper healthcare, but how will we design them to give informative causal explanations? Ideas from philosophy, model checking, and statistical testing can pave the way for the needed translational systems biology.

One morning, as Gregorina Samsa was waking up from anxious dreams, she discovered that she had become afflicted with certain mysterious flu-like symptoms that appeared without any warning. Equally irritating, this capricious metamorphosis seemed impervious to a rational explanation in terms of causes and effects. "What’s happened to me?" she thought. Before seeing a doctor, she decided to find out more about what might ail her. She logged on to a Web site where she annotated a timeline with what she could remember. Since March, she’d had more headaches than usual, and then in April she had begun to experience more fatigue after exercise, and as of July she had also experienced occasional lapses in memory.

Metaphors We Compute By:
Code is a story that explains how to solve a particular problem.

Programmers must be able to tell a story with their code, explaining how they solved a particular problem. Like writers, programmers must know their metaphors. Many metaphors will be able to explain a concept, but you must have enough skill to choose the right one that’s able to convey your ideas to future programmers who will read the code. Thus, you cannot use every metaphor you know. You must master the art of metaphor selection, of meaning amplification. You must know when to add and when to subtract. You will learn to revise and rewrite code as a writer does. Once there’s nothing else to add or remove, you have finished your work.

Metrics That Matter:
Critical but oft-neglected service metrics that every SRE and product owner should care about

Measure your site reliability metrics, set the right targets, and go through the work to measure the metrics accurately. Then, you’ll find that your service runs better, with fewer outages, and much more user adoption.

Mind Your State for Your State of Mind:
The interactions between storage and applications can be complex and subtle.

Applications have had an interesting evolution as they have moved into the distributed and scalable world. Similarly, storage and its cousin databases have changed side by side with applications. Many times, the semantics, performance, and failure models of storage and applications do a subtle dance as they change in support of changing business requirements and environmental challenges. Adding scale to the mix has really stirred things up. This article looks at some of these issues and their impact on systems.

Mobile Application Development: Web vs. Native:
Web apps are cheaper to develop and deploy than native apps, but can they match the native user experience?

A few short years ago, most mobile devices were, for want of a better word, "dumb." Sure, there were some early smartphones, but they were either entirely e-mail focused or lacked sophisticated touch screens that could be used without a stylus. Even fewer shipped with a decent mobile browser capable of displaying anything more than simple text, links, and maybe an image. This meant if you had one of these devices, you were either a businessperson addicted to e-mail or an alpha geek hoping that this would be the year of the smartphone.

Mobile Media: Making It a Reality:
Two prototype apps reveal the challenges in delivering mobile media services.

Many future mobile applications are predicated on the existence of rich, interactive media services. The promise and challenge of such services is to provide applications under the most hostile conditions - and at low cost to a user community that has high expectations. Context-aware services require information about who, where, when, and what a user is doing and must be delivered in a timely manner with minimum latency. This article reveals some of the current state-of-the-art "magic" and the research challenges.

Model-based Testing: Where Does It Stand?:
MBT has positive effects on efficiency and effectiveness, even if it only partially fulfills high expectations.

You have probably heard about MBT (model-based testing), but like many software-engineering professionals who have not used MBT, you might be curious about others’ experience with this test-design method. From mid-June 2014 to early August 2014, we conducted a survey to learn how MBT users view its efficiency and effectiveness. The 2014 MBT User Survey, a follow-up to a similar 2012 survey, was open to all those who have evaluated or used any MBT approach. Its 32 questions included some from a survey distributed at the 2013 User Conference on Advanced Automated Testing. Some questions focused on the efficiency and effectiveness of MBT, providing the figures that managers are most interested in.

Modeling People and Places with Internet Photo Collections:
Understanding the world from the sea of online photos

This article describes our work in using online photo collections to reconstruct information about the world and its inhabitants at both global and local scales. This work has been driven by the dramatic growth of social content-sharing Web sites, which have created immense online collections of user-generated visual data. Flickr.com alone currently hosts more than 6 billion images taken by more than 40 million unique users, while Facebook.com has said it grows by nearly 250 million photos every day.

Modern Performance Monitoring:
Today’s diverse and decentralized computer world demands new thinking about performance monitoring and analysis.

The modern Unix server floor can be a diverse universe of hardware from several vendors and software from several sources. Often, the personnel needed to resolve server floor performance issues are not available or, for security reasons, not allowed to be present at the very moment of occurrence. Even when, as luck might have it, the right personnel are actually present to witness a performance "event," the tools to measure and analyze the performance of the hardware and software have traditionally been sparse and vendor-specific.

Modern System Power Management:
Increasing demands for more power and increased efficiency are pressuring software and hardware developers to ask questions and look for answers.

The Advanced Configuration and Power Interface (ACPI) is the most widely used power and configuration interface for laptops, desktops, and server systems. It is also very complex, and its current specification weighs in at more than 500 pages. Needless to say, operating systems that choose to support ACPI require significant additional software support, up to and including fundamental OS architecture changes. The effort that ACPI’s definition and implementation has entailed is worth the trouble because of how much flexibility it gives to the OS (and ultimately the user) to control power management policy and implementation.

MongoDB’s JavaScript Fuzzer:
The fuzzer is for those edge cases that your testing didn’t catch.

As MongoDB becomes more feature-rich and complex with time, the need to develop more sophisticated methods for finding bugs grows as well. Three years ago, MongDB added a home-grown JavaScript fuzzer to its toolkit, and it is now our most prolific bug-finding tool, responsible for detecting almost 200 bugs over the course of two release cycles. These bugs span a range of MongoDB components from sharding to the storage engine, with symptoms ranging from deadlocks to data inconsistency. The fuzzer runs as part of the CI (continuous integration) system, where it frequently catches bugs in newly committed code.

Monitoring and Control of Large Systems with MonALISA:
MonALISA developers describe how it works, the key design principles behind it, and the biggest technical challenges in building it.

The HEP (high energy physics) group at the California Institute of Technology started developing the MonALISA (Monitoring Agents using a Large Integrated Services Architecture) framework in 2002, aiming to provide a distributed service system capable of controlling and optimizing large-scale, data-intensive applications. Its initial target field of applications is the grid systems and the networks supporting data processing and analysis for HEP collaborations. Our strategy in trying to satisfy the demands of data-intensive applications was to move to more synergetic relationships between the applications, computing, and storage facilities and the network infrastructure.

Monitoring in a DevOps World:
Perfect should never be the enemy of better.

Monitoring can seem quite overwhelming. The most important thing to remember is that perfect should never be the enemy of better. DevOps enables highly iterative improvement within organizations. If you have no monitoring, get something; get anything. Something is better than nothing, and if you’ve embraced DevOps, you’ve already signed up for making it better over time.

Monitoring, at Your Service:
Automated monitoring can increase the reliability and scalability of today’s online software services.

Internet services are becoming more and more a part of our daily lives. We derive value from them, depend on them, and are now beginning to assume their ubiquity as we do the phone system and electricity grid. The implementation of Internet services, though, is an unsolved problem, and Internet services remain far from fulfilling their potential in our world.

Multipath TCP:
Decoupled from IP, TCP is at last able to support multihomed hosts.

The Internet relies heavily on two protocols. In the network layer, IP (Internet Protocol) provides an unreliable datagram service and ensures that any host can exchange packets with any other host. Since its creation in the 1970s, IP has seen the addition of several features, including multicast, IPsec (IP security), and QoS (quality of service). The latest revision, IPv6 (IP version 6), supports 16-byte addresses.

Multitier Programming in Hop:
A first step toward programming 21st-century applications

The Web is becoming the richest platform on which to create computer applications. Its power comes from three elements: (1) modern Web browsers enable highly sophisticated GUIs with 3D, multimedia, fancy typesetting, etc.; (2) calling existing services through Web APIs makes it possible to develop sophisticated applications from independently available components; and (3) open data availability allows applications to access a wide set of information that was unreachable or that simply did not exist before. The combination of these three elements has already given birth to revolutionary applications such as Google Maps, radio podcasts, and social networks.

NUMA (Non-Uniform Memory Access): An Overview:
NUMA becomes more common because memory controllers get close to execution units on microprocessors.

NUMA (non-uniform memory access) is the phenomenon that memory at various points in the address space of a processor have different performance characteristics. At current processor speeds, the signal path length from the processor to memory plays a significant role. Increased signal path length not only increases latency to memory but also quickly becomes a throughput bottleneck if the signal path is shared by multiple processors. The performance differences to memory were noticeable first on large-scale systems where data paths were spanning motherboards or chassis. These systems required modified operating-system kernels with NUMA support that explicitly understood the topological properties of the system’s memory (such as the chassis in which a region of memory was located) in order to avoid excessively long signal path lengths.

National Internet Defense - Small States on the Skirmish Line:
Attacks in Estonia and Georgia highlight key vulnerabilities in national Internet infrastructure.

Despite the global and borderless nature of the Internet’s underlying protocols and driving philosophy, there are significant ways in which it remains substantively territorial. Nations have policies and laws that govern and attempt to defend "their Internet". This is far less palpable than a nation’s physical territory or even than "its air" or "its water". Cyberspace is still a much wilder frontier, hard to define and measure. Where its effects are noted and measurable, all too often they are hard to attribute to responsible parties.

Natural Language Translation at the Intersection of AI and HCI:
Old questions being answered with both AI and HCI

The fields of artificial intelligence (AI) and human-computer interaction (HCI) are influencing each other like never before. Widely used systems such as Google Translate, Facebook Graph Search, and RelateIQ hide the complexity of large-scale AI systems behind intuitive interfaces. But relations were not always so auspicious. The two fields emerged at different points in the history of computer science, with different influences, ambitions, and attendant biases. AI aimed to construct a rival, and perhaps a successor, to the human intellect. Early AI researchers such as McCarthy, Minsky, and Shannon were mathematicians by training, so theorem-proving and formal models were attractive research directions.

Net Neutrality: Unexpected Solution to Blockchain Scaling:
Cloud-delivery networks could dramatically improve blockchains’ scalability, but clouds must be provably neutral first.

Provably neutral clouds are undoubtedly a viable solution to blockchain scaling. By optimizing the transport layer, not only can the throughput be fundamentally scaled up, but the latency could be dramatically reduced. Indeed, the latency distribution in today’s data centers is already biased toward microsecond timescales for most of the flows, with millisecond timescales residing only at the tail of the distribution. There is no reason why a BDN point of presence would not be able to achieve a similar performance. Adding dedicated optical infrastructure among such BDN points of presence would further alleviate throughput and reduce latency, creating the backbone of an advanced BDN.

Network Applications Are Interactive:
The network era requires new models, with interactions instead of algorithms.

The miniaturization of devices and the prolific interconnectedness of these devices over high-speed wireless networks is completely changing how commerce is conducted. These changes (a.k.a. digital) will profoundly change how enterprises operate. Software is at the heart of this digital world, but the software toolsets and languages were conceived for the host-based era. The issues that already plague software practice (such as high defects, poor software productivity, information vulnerability, poor software project success rates, etc.) will be more profound with such an approach. It is time for software to be made simpler, secure, and reliable.

Network Forensics:
Good detective work means paying attention before, during, and after the attack.

The dictionary defines forensics as “the use of science and technology to investigate and establish facts in criminal or civil courts of law.” I am more interested, however, in the usage common in the computer world: using evidence remaining after an attack on a computer to determine how the attack was carried out and what the attacker did. The standard approach to forensics is to see what can be retrieved after an attack has been made, but this leaves a lot to be desired. The first and most obvious problem is that successful attackers often go to great lengths to ensure that they cover their trails.

Network Front-end Processors, Yet Again:
The history of NFE processors sheds light on the tradeoffs involved in designing network stack software.

The history of the NFE (network front-end) processor, currently best known as a TOE (TCP offload engine), extends all the way back to the Arpanet IMP (interface message processor) and possibly before. The notion is beguilingly simple: partition the work of executing communications protocols from the work of executing the "applications" that require the services of those protocols. That way, the applications and the network machinery can achieve maximum performance and efficiency, possibly taking advantage of special hardware performance assistance. While this looks utterly compelling on the whiteboard, architectural and implementation realities intrude, often with considerable force.

Network Virtualization: Breaking the Performance Barrier:
Shared I/O in virtualization platforms has come a long way, but performance concerns remain.

The recent resurgence in popularity of virtualization has led to its use in a growing number of contexts, many of which require high-performance networking. Consider server consolidation, for example. The efficiency of network virtualization directly impacts the number of network servers that can effectively be consolidated onto a single physical machine. Unfortunately, modern network virtualization techniques incur significant overhead, which limits the achievable network performance. We need new network virtualization techniques to realize the full benefits of virtualization in network-intensive domains.

Nine IM Accounts and Counting:
The key word with instant messaging today is interoperability.

Instant messaging has become nearly as ubiquitous as e-mail, in some cases far surpassing e-mail in popularity. But it has gone far beyond teenagers’ insular world to business, where it is becoming a useful communication tool. The problem, unlike e-mail, is that no common standard exists for IM, so users feel compelled to maintain multiple accounts, for example, AOL, Jabber, Yahoo, and MSN.

No Source Code? No Problem!:
What if you have to port a program, but all you have is a binary?

Typical software development involves one of two processes: the creation of new software to fit particular requirements or the modification (maintenance) of old software to fix problems or fit new requirements. These transformations happen at the source-code level. But what if the problem is not the maintenance of old software but the need to create a functional duplicate of the original? And what if the source code is no longer available?

Non-volatile Storage:
Implications of the Datacenter’s Shifting Center

For the entire careers of most practicing computer scientists, a fundamental observation has consistently held true: CPUs are significantly more performant and more expensive than I/O devices. The fact that CPUs can process data at extremely high rates, while simultaneously servicing multiple I/O devices, has had a sweeping impact on the design of both hardware and software for systems of all sizes, for pretty much as long as we’ve been building them.

Nonblocking Algorithms and Scalable Multicore Programming:
Exploring some alternatives to lock-based synchronization

Real-world systems with complicated quality-of-service guarantees may require a delicate balance between throughput and latency to meet operating requirements in a cost-efficient manner. The increasing availability and decreasing cost of commodity multicore and many-core systems make concurrency and parallelism increasingly necessary for meeting demanding performance requirements. Unfortunately, the design and implementation of correct, efficient, and scalable concurrent software is often a daunting task.

Not Your Father’s PBX?:
Integrating VoIP into the enterprise could mean the end of telecom business-as-usual.

Perhaps no piece of office equipment is more taken for granted than the common business telephone. The technology behind this basic communication device, however, is in the midst of a major transformation. Businesses are now converging their voice and data networks in order to simplify their network operations and take advantage of the new functional benefits and capabilities that a converged network delivers from greater productivity and cost savings to enhanced mobility.

OCaml for the Masses:
Why the next language you learn should be functional

Functional programming is an old idea with a distinguished history. Lisp, a functional language inspired by Alonzo Church’s lambda calculus, was one of the first programming languages developed at the dawn of the computing age. Statically typed functional languages such as OCaml and Haskell are newer, but their roots go deep.

ORM in Dynamic Languages:
O/R mapping frameworks for dynamic languages such as Groovy provide a different flavor of ORM that can greatly simplify application code.

A major component of most enterprise applications is the code that transfers objects in and out of a relational database. The easiest solution is often to use an ORM (object-relational mapping) framework, which allows the developer to declaratively define the mapping between the object model and database schema and express database-access operations in terms of objects. This high-level approach significantly reduces the amount of database-access code that needs to be written and boosts developer productivity.

Ode to a Sailor:
sailor, fleeting mood image of you; all sailor in bear grace, rough hands and poetic dream;

In memory of Jim Gray

Of Processors and Processing:
There’s more than one way to DSP

Digital signal processing is a stealth technology. It is the core enabling technology in everything from your cellphone to the Mars Rover. It goes much further than just enabling a one-time breakthrough product. It provides ever-increasing capability; compare the performance gains made by dial-up modems with the recent performance gains of DSL and cable modems. Remarkably, digital signal processing has become ubiquitous with little fanfare, and most of its users are not even aware of what it is.

On Mapping Alogrithms to DSP Architectures:
Knowledge of both the algorithm and target architecture is crucial.

Our complex world is characterized by representation, transmission, and storage of information - and information is mostly processed in digital form. With the advent of DSPs (digital signal processors), engineers are able to implement complex algorithms with relative ease. Today we find DSPs all around us - in cars, digital cameras, MP3 and DVD players, modems, and so forth. Their widespread use and deployment in complex systems has triggered a revolution in DSP architectures, which in turn has enabled engineers to implement algorithms of ever-increasing complexity.

On Plug-ins and Extensible Architectures:
Extensible application architectures such as Eclipse offer many advantages, but one must be careful to avoid “plug-in hell.”

In a world of increasingly complex computing requirements, we as software developers are continually searching for that ultimate, universal architecture that allows us to productively develop high-quality applications. This quest has led to the adoption of many new abstractions and tools. Some of the most promising recent developments are the new pure plug-in architectures. What began as a callback mechanism to extend an application has become the very foundation of applications themselves. Plug-ins are no longer just add-ons to applications; today’s applications are made entirely of plug-ins.

One Step Ahead:
Security vulnerabilities abound, but a few simple steps can minimize your risk.

Every day IT departments are involved in an ongoing struggle against hackers trying to break into corporate networks. A break-in can carry a hefty price: loss of valuable information, tarnishing of the corporate image and brand, service interruption, and hundreds of resource hours of recovery time. Unlike other aspects of information technology, security is adversarial. It pits IT departments against hackers.

Online Algorithms in High-frequency Trading:
The challenges faced by competing HFT algorithms

HFT (high-frequency trading) has emerged as a powerful force in modern financial markets. Only 20 years ago, most of the trading volume occurred in exchanges such as the New York Stock Exchange, where humans dressed in brightly colored outfits would gesticulate and scream their trading intentions. Nowadays, trading occurs mostly in electronic servers in data centers, where computers communicate their trading intentions through network messages. This transition from physical exchanges to electronic platforms has been particularly profitable for HFT firms, which invested heavily in the infrastructure of this new environment.

Online Event Processing:
Achieving consistency where distributed transactions have failed

Support for distributed transactions across heterogeneous storage technologies is either nonexistent or suffers from poor operational and performance characteristics. In contrast, OLEP is increasingly used to provide good performance and strong consistency guarantees in such settings. In data systems it is very common for logs to be used as internal implementation details. The OLEP approach is different: it uses event logs, rather than transactions, as the primary application programming model for data management. Traditional databases are still used, but their writes come from a log rather than directly from the application. The use of OLEP is not simply pragmatism on the part of developers, but rather it offers a number of advantages.

Oops! Coping with Human Error in IT Systems:
Errors Happen. How to Deal.

Human operator error is one of the most insidious sources of failure and data loss in today’s IT environments. In early 2001, Microsoft suffered a nearly 24-hour outage in its Web properties as a result of a human error made while configuring a name resolution system. Later that year, an hour of trading on the Nasdaq stock exchange was disrupted because of a technicians mistake while testing a development system. More recently, human error has been blamed for outages in instant messaging networks, for security and privacy breaches, and for banking system failures.

Open Source to the Core:
Using open source in real-world software products: The good, the bad and the ugly

The open source development model is not exactly new. Individual engineers have been using open source as a collaborative development methodology for decades. Now that it has come to the attention of upper and middle management, however, it’s finally being openly acknowledged as a commercial engineering force-multiplier and important option for avoiding significant software development costs.

Open Spectrum:
A Path to Ubiquitous Connectivity

Just as open standards and open software rocked the networking and computing industry, open spectrum is poised to be a disruptive force in the use of radio spectrum for communications. At the same time, open spectrum will be a major element that helps continue the Internet’s march to integrate and facilitate all electronic communications with open standards and commodity hardware.

Open vs. Closed:
Which source is more secure?

There is no better way to start an argument among a group of developers than proclaiming Operating System A to be "more secure" than Operating System B. I know this from first-hand experience, as previous papers I have published on this topic have led to reams of heated e-mails directed at me - including some that were, quite literally, physically threatening. Despite the heat (not light!) generated from attempting to investigate the relative security of different software projects, investigate we must.

Open-source Firmware:
Step into the world behind the kernel.

Open-source firmware can help bring computing to a more secure place by making the actions of firmware more visible and less likely to do harm. This article’s goal is to make readers feel empowered to demand more from vendors who can help drive this change.

OpenFlow: A Radical New Idea in Networking:
An open standard that enables software-defined networking

Computer networks have historically evolved box by box, with individual network elements occupying specific ecological niches as routers, switches, load balancers, NATs (network address translations), or firewalls. Software-defined networking proposes to overturn that ecology, turning the network as a whole into a platform and the individual network elements into programmable entities. The apps running on the network platform can optimize traffic flows to take the shortest path, just as the current distributed protocols do, but they can also optimize the network to maximize link utilization, create different reachability domains for different users, or make device mobility seamless.

Optimizations in C++ Compilers:
A practical journey

There’s a tradeoff to be made in giving the compiler more information: it can make compilation slower. Technologies such as link time optimization can give you the best of both worlds. Optimizations in compilers continue to improve, and upcoming improvements in indirect calls and virtual function dispatch might soon lead to even faster polymorphism.

Orchestrating an Automated Test Lab:
Composing a score can help us manage the complexity of testing distributed apps.

Networking and the Internet are encouraging increasing levels of interaction and collaboration between people and their software. Whether users are playing games or composing legal documents, their applications need to manage the complex interleaving of actions from multiple machines over potentially unreliable connections. As an example, Silicon Chalk is a distributed application designed to enhance the in-class experience of instructors and students. Its distributed nature requires that we test with multiple machines. Manual testing is too tedious, expensive, and inconsistent to be effective. While automating our testing, however, we have found it very labor intensive to maintain a set of scripts describing each machine’s portion of a given test.

Order from Chaos:
Will ontologies help you structure your semi-structured data?

There is probably little argument that the past decade has brought the “big bang” in the amount of online information available for processing by humans and machines. Two of the trends that it spurred (among many others) are: first, there has been a move to more flexible and fluid (semi-structured) models than the traditional centralized relational databases that stored most of the electronic data before; second, today there is simply too much information available to be processed by humans, and we really need help from machines.

Other People’s Data:
Companies have access to more types of external data than ever before. How can they integrate it most effectively?

Every organization bases some of its critical decisions on external data sources. In addition to traditional flat file data feeds, Web services and Web pages are playing an increasingly important role in data warehousing. The growth of Web services has made data feeds easily consumable at the departmental and even end-user levels. There are now more than 1,500 publicly available Web services and thousands of data mashups ranging from retail sales data to weather information to United States census data. These mashups are evidence that when users need information, they will find a way to get it.

Outsourcing: Devising a Game Plan:
What types of projects make good candidates for outsourcing?

Your CIO just summoned you to duty by handing off the decision-making power about whether to outsource next years big development project to rewrite the internal billing system. That’s quite a daunting task! How can you possibly begin to decide if outsourcing is the right option for your company? There are a few strategies that you can follow to help you avoid the pitfalls of outsourcing and make informed decisions. Outsourcing is not exclusively a technical issue, but it is a decision that architects or development managers are often best qualified to make because they are in the best position to know what technologies make sense to keep in-house.

Parallel Processing with Promises:
A simple method of writing a collaborative system

In today’s world, there are many reasons to write concurrent software. The desire to improve performance and increase throughput has led to many different asynchronous techniques. The techniques involved, however, are generally complex and the source of many subtle bugs, especially if they require shared mutable state. If shared state is not required, then these problems can be solved with a better abstraction called promises. These allow programmers to hook asynchronous function calls together, waiting for each to return success or failure before running the next appropriate function in the chain.

Parallel Programming with Transactional Memory:
While sometimes even writing regular, single-threaded programs can be quite challenging, trying to split a program into multiple pieces that can be executed in parallel adds a whole dimension of additional problems. Drawing upon the transaction concept familiar to most programmers, transactional memory was designed to solve some of these problems and make parallel programming easier. Ulrich Drepper from Red Hat shows us how it’s done.

With the speed of individual cores no longer increasing at the rate we came to love over the past decades, programmers have to look for other ways to increase the speed of our ever-more-complicated applications. The functionality provided by the CPU manufacturers is an increased number of execution units, or CPU cores.

Passing a Language through the Eye of a Needle:
How the embeddability of Lua impacted its design

Scripting languages are an important element in the current landscape of programming languages. A key feature of a scripting language is its ability to integrate with a system language. This integration takes two main forms: extending and embedding. In the first form, you extend the scripting language with libraries and functions written in the system language and write your main program in the scripting language. In the second form, you embed the scripting language in a host program (written in the system language) so that the host can run scripts and call functions defined in the scripts; the main program is the host program.

Passively Measuring TCP Round-trip Times:
A close look at RTT measurements with TCP

Measuring and monitoring network RTT (round-trip time) is important for multiple reasons: it allows network operators and end users to understand their network performance and help optimize their environment, and it helps businesses understand the responsiveness of their services to sections of their user base.

Patching the Enterprise:
Organizations of all sizes are spending considerable efforts on getting patch management right - their businesses depend on it.

Software patch management has grown to be a business-critical issue—from both a risk and a financial management perspective. According to a recent Aberdeen Group study, corporations spent more than $2 billion in 2002 on patch management for operating systems.1 Gartner research further notes the cost of operating a well-managed PC was approximately $2,000 less annually than that of an unmanaged PC.2 You might think that with critical mass and more sophisticated tools, the management cost per endpoint in large organizations would be lower, though in reality this may not be the case.

People and Process:
Minimizing the pain of business process change

When Mike Hammer and I published Reengineering the Corporation in 1992, we understood the impact that real business process change would have on people. I say "real" process change, because managers have used the term reengineering to describe any and all corporate change programs. One misguided executive told me that his company did not know how to do real reengineering; so it just downsized large departments and business units, and expected that the people who were left would figure out how to get their work done. Sadly, this is how some companies still practice process redesign: leaving people overworked and demoralized, while customers experience bad service and poor quality.

People in Our Software:
A person-centric approach could make software come alive, but at what cost?

People are not well represented in today’s software. With the exception of IM (instant messaging) clients, today’s applications offer few clues that people are actually living beings. Static strings depict things associated with people like e-mail addresses, phone numbers, and home-page URLs. Applications also tend to show the same information about a person, no matter who is viewing it.

Performance Anti-Patterns:
Want your apps to run faster? Here’s what not to do.

Performance pathologies can be found in almost any software, from user to kernel, applications, drivers, etc. At Sun we’ve spent the last several years applying state-of-the-art tools to a Unix kernel, system libraries, and user applications, and have found that many apparently disparate performance problems in fact have the same underlying causes. Since software patterns are considered abstractions of positive experience, we can talk about the various approaches that led to these performance problems as anti-patterns: something to be avoided rather than emulated.

Persistent Memory Programming on Conventional Hardware:
The persistent memory style of programming can dramatically simplify application software.

Driven by the advent of byte-addressable non-volatile memory, the persistent memory style of programming will gain traction among developers, taking its rightful place alongside existing paradigms for managing persistent application state. Until NVM becomes available on all computers, developers can use the techniques presented in this article to enjoy the benefits of persistent memory programming on conventional hardware.

Pervasive, Dynamic Authentication of Physical Items:
The use of silicon PUF circuits

Authentication of physical items is an age-old problem. Common approaches include the use of bar codes, QR codes, holograms, and RFID (radio-frequency identification) tags. Traditional RFID tags and bar codes use a public identifier as a means of authenticating. A public identifier, however, is static: it is the same each time when queried and can be easily copied by an adversary. Holograms can also be viewed as public identifiers: a knowledgeable verifier knows all the attributes to inspect visually. It is difficult to make hologram-based authentication pervasive; a casual verifier does not know all the attributes to look for.

Phishing Forbidden:
Current anti-phishing technologies prevent users from taking the bait.

Phishing is a significant risk facing Internet users today. Through e-mails or instant messages, users are led to counterfeit Web sites designed to trick them into divulging usernames, passwords, account numbers, and personal information. It is up to the user to ensure the authenticity of the Web site. Browsers provide some tools, but these are limited by at least three issues.

Playing for Keeps:
Will security threats bring an end to general-purpose computing?

Inflection points come at you without warning and quickly recede out of reach. We may be nearing one now. If so, we are now about to play for keeps, and “we” doesn’t mean just us security geeks. If anything, it’s because we security geeks have not worked the necessary miracles already that an inflection point seems to be approaching at high velocity.

Postmortem Debugging in Dynamic Environments:
Modern dynamic languages lack tools for understanding software failures.

Despite the best efforts of software engineers to produce high-quality software, inevitably some bugs escape even the most rigorous testing process and are first encountered by end users. When this happens, such failures must be understood quickly, the underlying bugs fixed, and deployments patched to avoid another user (or the same one) running into the same problem again.

Power-Efficient Software:
Power-manageable hardware can help save energy, but what can software developers do to address the problem?

The rate at which power-management features have evolved is nothing short of amazing. Today almost every size and class of computer system, from the smallest sensors and handheld devices to the "big iron" servers in data centers, offers a myriad of features for reducing, metering, and capping power consumption. Without these features, fan noise would dominate the office ambience, and untethered laptops would remain usable for only a few short hours (and then only if one could handle the heat), while data-center power and cooling costs and capacity would become unmanageable.

Powering Down:
Smart power management is all about doing more with the resources we have.

Power management is a topic of interest to everyone. In the beginning there was the desktop computer. It ran at a fixed speed and consumed less power than the monitor it was plugged into. Where computers were portable, their sheer size and weight meant that you were more likely to be limited by physical strength than battery life. It was not a great time for power management. Now consider the present. Laptops have increased in speed by more than 5,000 times. Battery capacity, sadly, has not. With hardware becoming increasingly mobile, however, users are demanding that battery life start matching the way they work.

Principles of Robust Timing over the Internet:
The key to synchronizing clocks over networks is taming delay variability.

Everyone, and most everything, needs a clock, and computers are no exception. Clocks tend to drift off if left to themselves, however, so it is necessary to bring them to heel periodically through synchronizing to some other reference clock of higher accuracy. An inexpensive and convenient way to do this is over a computer network.

Privacy, Anonymity, and Big Data in the Social Sciences:
Quality social science research and the privacy of human subjects requires trust.

Open data has tremendous potential for science, but, in human subjects research, there is a tension between privacy and releasing high-quality open data. Federal law governing student privacy and the release of student records suggests that anonymizing student data protects student privacy. Guided by this standard, we de-identified and released a data set from 16 MOOCs (massive open online courses) from MITx and HarvardX on the edX platform. In this article, we show that these and other de-identification procedures necessitate changes to data sets that threaten replication and extension of baseline analyses. To balance student privacy and the benefits of open data, we suggest focusing on protecting privacy without anonymizing data by instead expanding policies that compel researchers to uphold the privacy of the subjects in open data sets.

Probing Biomolecular Machines with Graphics Processors:
The evolution of GPU processors and programming tools is making advanced simulation and analysis techniques accessible to a growing community of biomedical scientists.

Computer simulation has become an integral part of the study of the structure and function of biological molecules. For years, parallel computers have been used to conduct these computationally demanding simulations and to analyze their results. These simulations function as a "computational microscope," allowing the scientist to observe details of molecular processes too small, fast, or delicate to capture with traditional instruments. Over time, commodity GPUs (graphics processing units) have evolved into massively parallel computing devices, and more recently it has become possible to program them in dialects of the popular C/C++ programming languages.

Productivity in Parallel Programming: A Decade of Progress:
Looking at the design and benefits of X10

In 2002 DARPA (Defense Advanced Research Projects Agency) launched a major initiative in HPCS (high-productivity computing systems). The program was motivated by the belief that the utilization of the coming generation of parallel machines was gated by the difficulty of writing, debugging, tuning, and maintaining software at peta scale.

Programmers Are People, too:
Programming language and API designers can learn a lot from the field of human-factors design.

I would like to start out this article with an odd, yet surprisingly uncontroversial assertion, which is this: programmers are human. I wish to use this as a premise to explore how to improve the programmer’s lot. So, please, no matter your opinion on the subject, grant me this assumption for the sake of argument.

Programming Without a Net:
Embedded systems programming presents special challenges to engineers unfamiliar with that environment.

Embedded systems programming presents special challenges to engineers unfamiliar with that environment. In some ways it is closer to working inside an operating system kernel than writing an application for use on the desktop. Here’s what to look out for.

Provenance in Sensor Data Management:
A cohesive, independent solution for bringing provenance to scientific research

In today’s information-driven workplaces, data is constantly being moved around and undergoing transformation. The typical business-as-usual approach is to use e-mail attachments, shared network locations, databases, and more recently, the cloud. More often than not, there are multiple versions of the data sitting in different locations, and users of this data are confounded by the lack of metadata describing its provenance or in other words, its lineage. The ProvDMS project at the Oak Ridge National Laboratory (ORNL) described in this article aims to solve this issue in the context of sensor data.

Proving the Correctness of Nonblocking Data Structures:
So you’ve decided to use a nonblocking data structure, and now you need to be certain of its correctness. How can this be achieved?

Nonblocking synchronization can yield astonishing results in terms of scalability and realtime response, but at the expense of verification state space.

Purpose-Built Languages:
While often breaking the rules of traditional language design, the growing ecosystem of purpose-built "little" languages is an essential part of systems development.

In my college computer science lab, two eternal debates flourished during breaks from long nights of coding and debugging: "emacs versus vi?"; and "what is the best programming language?" Later, as I began my career in industry, I noticed that the debate over programming languages was also going on in the hallways of Silicon Valley campuses. It was the ’90s, and at Sun many of us were watching Java claim significant mindshare among developers, particularly those previously developing in C or C++.

Putting It All Together:
Component integration is one of the tough challenges in embedded system design. Designers search for conservative design styles and reliable techniques for interfacing and verification.

With the growing complexity of embedded systems, more and more parts of a system are reused or supplied, often from external sources. These parts range from single hardware components or software processes to hardware-software (HW-SW) subsystems. They must cooperate and share resources with newly developed parts such that all of the design constraints are met. This, simply speaking, is the integration task, which ideally should be a plug-and-play procedure. This does not happen in practice, however, not only because of incompatible interfaces and communication standards but also because of specialization.

Quality Assurance: Much More than Testing:
Good QA is not only about technology, but also methods and approaches.

Quality assurance isn’t just testing, or analysis, or wishful thinking. Although it can be boring, difficult, and tedious, QA is nonetheless essential. Ensuring that a system will work when delivered requires much planning and discipline. Convincing others that the system will function properly requires even more careful and thoughtful effort. QA is performed through all stages of the project, not just slapped on at the end. It is a way of life.

Rate-limiting State:
The edge of the Internet is an unruly place

By design, the Internet core is dumb, and the edge is smart. This design decision has enabled the Internet’s wildcat growth, since without complexity the core can grow at the speed of demand. On the downside, the decision to put all smartness at the edge means we’re at the mercy of scale when it comes to the quality of the Internet’s aggregate traffic load. Not all device and software builders have the skills and the quality assurance budgets that something the size of the Internet deserves.

Reading, Writing, and Code:
The key to writing readable code is developing good coding style.

Forty years ago, when computer programming was an individual experience, the need for easily readable code wasn’t on any priority list. Today, however, programming usually is a team-based activity, and writing code that others can easily decipher has become a necessity. Creating and developing readable code is not as easy as it sounds.

Real-World Concurrency:
In this look at how concurrency affects practitioners in the real world, Cantrill and Bonwick argue that much of the anxiety over concurrency is unwarranted.

Software practitioners today could be forgiven if recent microprocessor developments have given them some trepidation about the future of software. While Moore’s law continues to hold (that is, transistor density continues to double roughly every 18 months), as a result of both intractable physical limitations and practical engineering considerations, that increasing density is no longer being spent on boosting clock rate. Instead, it is being used to put multiple CPU cores on a single CPU die.

Real-world String Comparison:
How to handle Unicode sequences correctly

In many languages a string comparison is a pitfall for beginners. With any Unicode string as input, a comparison often causes problems even for advanced users. The semantic equivalence of different characters in Unicode requires a normalization of the strings before comparing them. This article shows how to handle Unicode sequences correctly. The comparison of two strings for equality often raises questions concerning the difference between comparison by value, comparison of object references, strict equality, and loose equality. The most important aspect is semantic equivalence.

Realtime Computer Vision with OpenCV:
Mobile computer-vision technology will soon become as ubiquitous as touch interfaces.

Computer vision is a rapidly growing field devoted to analyzing, modifying, and high-level understanding of images. Its objective is to determine what is happening in front of a camera and use that understanding to control a computer or robotic system, or to provide people with new images that are more informative or aesthetically pleasing than the original camera images. Application areas for computer-vision technology include video surveillance, biometrics, automotive, photography, movie production, Web search, medicine, augmented reality gaming, new user interfaces, and many more.

Realtime GPU Audio:
Finite difference-based sound synthesis using graphics processors

Today’s CPUs are capable of supporting realtime audio for many popular applications, but some compute-intensive audio applications require hardware acceleration. This article looks at some realtime sound-synthesis applications and shares the authors’ experiences implementing them on GPUs (graphics processing units).

Realtime Garbage Collection:
It’s now possible to develop realtime systems using Java.

Traditional computer science deals with the computation of correct results. Realtime systems interact with the physical world, so they have a second correctness criterion: they have to compute the correct result within a bounded amount of time. Simply building functionally correct software is hard enough. When timing is added to the requirements, the cost and complexity of building the software increase enormously.

Reconfigurable Future:
The ability to produce cheaper, more compact chips is a double-edged sword.

Predicting the future is notoriously hard. Sometimes I feel that the only real guarantee is that the future will happen, and that someone will point out how it’s not like what was predicted. Nevertheless, we seem intent on trying to figure out what will happen, and worse yet, recording these views so they can be later used against us. So here I go... Scaling has been driving the whole electronics industry, allowing it to produce chips with more transistors at a lower cost.

Reliable Cron across the Planet:
...or How I stopped worrying and learned to love time

This article describes Google’s implementation of a distributed Cron service, serving the vast majority of internal teams that need periodic scheduling of compute jobs. During its existence, we have learned many lessons on how to design and implement what might seem like a basic service. Here, we discuss the problems that distributed Crons face and outline some potential solutions.

Rethinking Passwords:
Our authentication system is lacking. Is improvement possible?

There is an authentication plague upon the land. We have to claim and assert our identity repeatedly to a host of authentication trolls, each jealously guarding an Internet service of some sort. Each troll has specific rules for passwords, and the rules vary widely and incomprehensibly.

Returning Control to the Programmer:
Exposing SIMD units within interpreted languages could simplify programs and unleash floods of untapped processor power.

Server and workstation hardware architecture is continually improving, yet interpreted languages have failed to keep pace with the proper utilization of modern processors. SIMD (single instruction, multiple data) units are available in nearly every current desktop and server processor and are greatly underutilized, especially with interpreted languages. If multicore processors continue their current growth pattern, interpreted-language performance will begin to fall behind, since current native compilers and languages offer better automated SIMD optimization and direct SIMD mapping support.

Revealing the Critical Role of Human Performance in Software:
It’s time to revise our appreciation of the human side of Internet-facing software systems.

Understanding, supporting, and sustaining the capabilities above the line of representation require all stakeholders to be able to continuously update and revise their models of how the system is messy and yet usually manages to work. This kind of openness to continually reexamine how the system really works requires expanding the efforts to learn from incidents.

Revisiting Network I/O APIs: The netmap Framework:
It is possible to achieve huge performance improvements in the way packet processing is done on modern operating systems.

Today 10-gigabit interfaces are used more and more in datacenters and servers. On these links, packets flow as fast as one every 67.2 nanoseconds, yet modern operating systems can take 10-20 times longer just to move one packet between the wire and the application. We can do much better, not with more powerful hardware but by revising architectural decisions made long ago regarding the design of device drivers and network stacks.

Rules for Mobile Performance Optimization:
An overview of techniques to speed page loading

Performance has always been crucial to the success of Web sites. A growing body of research has proven that even small improvements in page-load times lead to more sales, more ad revenue, more stickiness, and more customer satisfaction for enterprises ranging from small e-commerce shops to megachains such as Walmart.

SAGE: Whitebox Fuzzing for Security Testing:
SAGE has had a remarkable impact at Microsoft.

Most ACM Queue readers might think of "program verification research" as mostly theoretical with little impact on the world at large. Think again. If you are reading these lines on a PC running some form of Windows (like 93-plus percent of PC users--that is, more than a billion people), then you have been affected by this line of work--without knowing it, which is precisely the way we want it to be.

SIP: Basics and Beyond:
More than just a simple telephony application protocol, SIP is a framework for developing communications systems.

Chances are you’re already using SIP (Session Initiation Protocol). It is one of the key innovations driving the current evolution of communications systems. Its first major use has been signaling in Internet telephony. Large carriers have been using SIP inside their networks for interconnect and trunking across long distances for several years. If you’ve made a long-distance call, part of that call probably used SIP.

Scalability Techniques for Practical Synchronization Primitives:
Designing locking primitives with performance in mind

In an ideal world, applications are expected to scale automatically when executed on increasingly larger systems. In practice, however, not only does this scaling not occur, but it is common to see performance actually worsen on those larger systems.

Scalable Parallel Programming with CUDA:
Is CUDA the parallel programming model that application developers have been waiting for?

The advent of multicore CPUs and manycore GPUs means that mainstream processor chips are now parallel systems. Furthermore, their parallelism continues to scale with Moore’s law. The challenge is to develop mainstream application software that transparently scales its parallelism to leverage the increasing number of processor cores, much as 3D graphics applications transparently scale their parallelism to manycore GPUs with widely varying numbers of cores.

Scalable SQL:
How do large-scale sites and applications remain SQL-based?

One of the leading motivators for NoSQL innovation is the desire to achieve very high scalability to handle the vagaries of Internet-size workloads. Yet many big social Web sites and many other Web sites and distributed tier 1 applications that require high scalability reportedly remain SQL-based for their core data stores and services. The question is, how do they do it?

Scaling Existing Lock-based Applications with Lock Elision:
Lock elision enables existing lock-based programs to achieve the performance benefits of nonblocking synchronization and fine-grain locking with minor software engineering effort.

Multithreaded applications take advantage of increasing core counts to achieve high performance. Such programs, however, typically require programmers to reason about data shared among multiple threads. Programmers use synchronization mechanisms such as mutual-exclusion locks to ensure correct updates to shared data in the presence of accesses from multiple threads. Unfortunately, these mechanisms serialize thread accesses to the data and limit scalability.

Scaling Synchronization in Multicore Programs:
Advanced synchronization methods can boost the performance of multicore software.

Designing software for modern multicore processors poses a dilemma. Traditional software designs, in which threads manipulate shared data, have limited scalability because synchronization of updates to shared data serializes threads and limits parallelism. Alternative distributed software designs, in which threads do not share mutable data, eliminate synchronization and offer better scalability. But distributed designs make it challenging to implement features that shared data structures naturally provide, such as dynamic load balancing and strong consistency guarantees, and are simply not a good fit for every program. Often, however, the performance of shared mutable data structures is limited by the synchronization methods in use today, whether lock-based or lock-free.

Scaling in Games & Virtual Worlds:
Online games and virtual worlds have familiar scaling requirements, but don’t be fooled: everything you know is wrong.

I used to be a systems programmer, working on infrastructure used by banks, telecom companies, and other engineers. I worked on operating systems. I worked on distributed middleware. I worked on programming languages. I wrote tools. I did all of the things that hard-core systems programmers do.

Schema.org: Evolution of Structured Data on the Web:
Big data makes common schemas even more necessary.

Separation between content and presentation has always been one of the important design aspects of the Web. Historically, however, even though most Web sites were driven off structured databases, they published their content purely in HTML. Services such as Web search, price comparison, reservation engines, etc. that operated on this content had access only to HTML. Applications requiring access to the structured data underlying these Web pages had to build custom extractors to convert plain HTML into structured data. These efforts were often laborious and the scrapers were fragile and error-prone, breaking every time a site changed its layout.

Scrum Essentials Cards:
Experiences of Scrum Teams Improving with Essence

This article presents a series of examples and case studies on how people have used the Scrum Essentials cards to benefit their teams and improve how they work. Scrum is one of the most popular agile frameworks used successfully all over the world. It has been taught and used for 15-plus years. It is by far the most-used practice when developing software, and it has been generalized to be applicable for not just software but all kinds of products. It has been taught to millions of developers, all based on the Scrum Guide.

Search Considered Integral:
A combination of tagging, categorization, and navigation can help end-users leverage the power of enterprise search.

Most corporations must leverage their data for competitive advantage. The volume of data available to a knowledge worker has grown dramatically over the past few years, and, while a good amount lives in large databases, an important subset exists only as unstructured or semi-structured data. Without the right systems, this leads to a continuously deteriorating signal-to-noise ratio, creating an obstacle for busy users trying to locate information quickly. Three flavors of enterprise search solutions help improve knowledge discovery.

Searching vs. Finding:
Why systems need knowledge to find what you really want

Finding information and organizing it so that it can be found are two key aspects of any company’s knowledge management strategy. Nearly everyone is familiar with the experience of searching with a Web search engine and using a search interface to search a particular Web site once you get there. (You may have even noticed that the latter often doesn’t work as well as the former.) After you have a list of hits, you typically spend a significant amount of time following links, waiting for pages to download, reading through a page to see if it has what you want, deciding that it doesn’t, backing up to try another link, deciding to try another way to phrase your request, et cetera.

Securing Elasticity in the Cloud:
Elastic computing has great potential, but many security challenges remain.

As somewhat of a technology-hype curmudgeon, I was until very recently in the camp that believed cloud computing was not much more than the latest marketing-driven hysteria for an idea that has been around for years. Outsourced IT infrastructure services, aka IaaS (Infrastructure as a Service), has been around since at least the 1980s, delivered by the telecommunication companies and major IT outsourcers. Hosted applications, aka PaaS (Platform as a Service) and SaaS (Software as a Service), were in vogue in the 1990s in the form of ASPs (application service providers).

Securing the Network Time Protocol:
Crackers discover how to use NTP as a weapon for abuse.

In the late 1970s David L. Mills began working on the problem of synchronizing time on networked computers, and NTP (Network Time Protocol) version 1 made its debut in 1980. This was at a time when the net was a much friendlier place - the ARPANET days. NTP version 2 appeared approximately a year later, about the same time as CSNET (Computer Science Network). NSFNET (National Science Foundation Network) launched in 1986. NTP version 3 showed up in 1993.

Securing the Tangled Web:
Preventing script injection vulnerabilities through software design

Script injection vulnerabilities are a bane of Web application development: deceptively simple in cause and remedy, they are nevertheless surprisingly difficult to prevent in large-scale Web development.

Security - Problem Solved?:
Solutions to many of our security problems already exist, so why are we still so vulnerable?

There are plenty of security problems that have solutions. Yet, our security problems don’t seem to be going away. What’s wrong here? Are consumers being offered snake oil and rejecting it? Are they not adopting solutions they should be adopting? Or, is there something else at work, entirely? We’ll look at a few places where the world could easily be a better place, but isn’t, and build some insight as to why.

Security Analysis of SMS as a Second Factor of Authentication:
The challenges of multifactor authentication based on SMS, including cellular security deficiencies, SS7 exploits, and SIM swapping

Despite their popularity and ease of use, SMS-based authentication tokens are arguably one of the least secure forms of two-factor authentication. This does not imply, however, that it is an invalid method for securing an online account. The current security landscape is very different from that of two decades ago. Regardless of the critical nature of an online account or the individual who owns it, using a second form of authentication should always be the default option, regardless of the method chosen.

Security Collapse in the HTTPS Market:
Assessing legal and technical solutions to secure HTTPS

HTTPS (Hypertext Transfer Protocol Secure) has evolved into the de facto standard for secure Web browsing. Through the certificate-based authentication protocol, Web services and Internet users first authenticate one another ("shake hands") using a TLS/SSL certificate, encrypt Web communications end-to-end, and show a padlock in the browser to signal that a communication is secure. In recent years, HTTPS has become an essential technology to protect social, political, and economic activities online.

Security in the Browser:
Web browsers leave users vulnerable to an ever-growing number of attacks. Can we make them secure while preserving their usability?

Sealed in a depleted uranium sphere at the bottom of the ocean. That’s the often-mentioned description of what it takes to make a computer reasonably secure. Obviously, in the Internet age or any other, such a machine would be fairly useless.

Security is Harder than You Think:
It’s not just about the buffer overflow.

Many developers see buffer overflows as the biggest security threat to software and believe that there is a simple two-step process to secure software: switch from C or C++ to Java, then start using SSL (Secure Sockets Layer) to protect data communications. It turns out that this naïve tactic isn’t sufficient. In this article, we explore why software security is harder than people expect, focusing on the example of SSL.

Security: The Root of the Problem:
Why is it we can’t seem to produce secure, high-quality code?

Security bug? My programming language made me do it! It doesn’t seem that a day goes by without someone announcing a critical flaw in some crucial piece of software or other. Is software that bad? Are programmers so inept? What the heck is going on, and why is the problem getting worse instead of better?

Self-Healing Networks:
Wireless networks that fix their own broken communication links may speed up their widespread acceptance.

The obvious advantage to wireless communication over wired is, as they say in the real estate business, location, location, location. Individuals and industries choose wireless because it allows flexibility of location--whether that means mobility, portability, or just ease of installation at a fixed point. The challenge of wireless communication is that, unlike the mostly error-free transmission environments provided by cables, the environment that wireless communications travel through is unpredictable. Environmental radio-frequency (RF) "noise" produced by powerful motors, other wireless devices, microwaves--and even the moisture content in the air--can make wireless communication unreliable.

Self-Healing in Modern Operating Systems:
A few early steps show there’s a long (and bumpy) road ahead.

Driving the stretch of Route 101 that connects San Francisco to Menlo Park each day, billboard faces smilingly reassure me that all is well in computerdom in 2004. Networks and servers, they tell me, can self-defend, self-diagnose, self-heal, and even have enough computing power left over from all this introspection to perform their owner-assigned tasks.

Sender-side Buffers and the Case for Multimedia Adaptation:
A proposal to improve the performance and availability of streaming video and other time-sensitive media

The Internet/Web architecture has developed to the point where it is common for the most popular sites to operate at a virtually unlimited scale, and many sites now cater to hundreds of millions of unique users. Performance and availability are generally essential to attract and sustain such user bases. As such, the network and server infrastructure plays a critical role in the fierce competition for users. Web pages should load in tens to a few hundred milliseconds at most.

Sensible Authentication:
According to the author of Beyond Fear, it’s not enough to know who you are; you’ve got to prove it.

The problem with securing assets and their functionality is that, by definition, you don’t want to protect them from everybody. It makes no sense to protect assets from their owners, or from other authorized individuals (including the trusted personnel who maintain the security system). In effect, then, all security systems need to allow people in, even as they keep people out. Designing a security system that accurately identifies, authenticates, and authorizes trusted individuals is highly complex and filled with nuance, but critical to security.

Sentient Data Access via a Diverse Society of Devices:
Today’s ubiquitous computing environment cannot benefit from the traditional understanding of a hierarchical file system.

It has been more than ten years since such "information appliances" as ATMs and grocery store UPC checkout counters were introduced. For the office environment, Mark Weiser began to articulate the notion of UbiComp and identified some of the salient features of the trends in 1991. Embedded computation is also becoming widespread. Microprocessors, for example, are finding themselves embedded into seemingly conventional pens that remember what they have written. Anti-lock brake systems in cars are controlled by fuzzy logic.

Should You Upload or Ship Big Data to the Cloud?:
The accepted wisdom does not always hold true.

It is accepted wisdom that when the data you wish to move into the cloud is at terabyte scale and beyond, you are better off shipping it to the cloud provider, rather than uploading it. This article takes an analytical look at how shipping and uploading strategies compare, the various factors on which they depend, and under what circumstances you are better off shipping rather than uploading data, and vice versa. Such an analytical determination is important to make, given the increasing availability of gigabit-speed Internet connections, along with the explosive growth in data-transfer speeds supported by newer editions of drive interfaces such as SAS and PCI Express.

Sifting Through the Software Sandbox: SCM Meets QA:
Source control—it’s not just for tracking changes anymore.

Thanks to modern SCM (software configuration management) systems, when developers work on a codeline they leave behind a trail of clues that can reveal what parts of the code have been modified, when, how, and by whom. From the perspective of QA (quality assurance) and test engineers, is this all just “data,” or is there useful information that can improve the test coverage and overall quality of a product?

Simplicity Betrayed:
Emulating a video system shows how even a simple interface can be more complex—and capable—than it appears.

An emulator is a program that runs programs built for different computer architectures from the host platform that supports the emulator. Approaches differ, but most emulators simulate the original hardware in some way. At a minimum the emulator interprets the original CPU instructions and provides simulated hardware-level devices for input and output. For example, keyboard input is taken from the host platform and translated into the original hardware format, resulting in the emulated program "seeing" the same sequence of keystrokes. Conversely, the emulator will translate the original hardware screen format into an equivalent form on the host machine.

Simulators: Virtual Machines of the Past (and Future):
Has the time come to kiss that old iron goodbye?

Simulators are a form of “virtual machine” intended to address a simple problem: the absence of real hardware. Simulators for past systems address the loss of real hardware and preserve the usability of software after real hardware has vanished. Simulators for future systems address the variability of future hardware designs and facilitate the development of software before real hardware exists.

Sink or Swim: Know When It’s Time to Bail:
A diagnostic to help you measure organizational dysfunction and take action

There are endless survival challenges for newly created businesses. The degree to which a business successfully meets these challenges depends largely on the nature of the organization and the culture that evolves within it. That’s to say that while market size, technical quality, and product design are obviously crucial factors, company failures are typically rooted in some form of organizational dysfunction.

SoC: Software, Hardware, Nightmare, Bliss:
System-on-a-chip design offers great promise by shrinking an entire computer to a single chip. But with the promise come challenges that need to be overcome before SoC reaches its full potential.

System-on-a-chip (SoC) design methodology allows a designer to create complex silicon systems from smaller working blocks, or systems. By providing a method for easily supporting proprietary functionality in a larger context that includes many existing design pieces, SoC design opens the craft of silicon design to a much broader audience.

Social Bookmarking in the Enterprise:
Can your organization benefit from social bookmarking tools?

One of the greatest challenges facing people who use large information spaces is to remember and retrieve items that they have previously found and thought to be interesting. One approach to this problem is to allow individuals to save particular search strings to re-create the search in the future. Another approach has been to allow people to create personal collections of material. Collections of citations can be created manually by readers or through execution of (and alerting to) a saved search.

Social Perception:
Modeling human interaction for the next generation of communication services

Bob manages a team that designs and builds widgets. Life would be sweet, except that Bob’s team is distributed over three sites, located in three different time zones. Bob used to collect lots of frequent flyer miles traveling to attend meetings. Lately, however, business travel has evolved into a humanly degrading, wasteful ordeal. So Bob has invested in a high-bandwidth video communications system to cut down on business travel. Counting direct costs, the system was supposed to pay for itself within three months. There is a problem, however.

Software Development in Disruptive Times:
Creating a software solution with fast decision capability, agile project management, and extreme low-code technology

In this project, the challenge was to "deploy software faster than the coronavirus spread." In a project with such peculiar characteristics, several factors can influence success, but some clearly stand out: top management support, agility, understanding and commitment of the project team, and the technology used. Conventional development approaches and technologies would simply not be able to meet the requirements promptly.

Software Development with Code Maps:
Could those ubiquitous hand-drawn code diagrams become a thing of the past?

To better understand how professional software developers use visual representations of their code, we interviewed nine developers at Microsoft to identify common scenarios, and then surveyed more than 400 developers to understand the scenarios more deeply.

Software Needs Seatbelts and Airbags:
Finding and fixing bugs in deployed software is difficult and time-consuming. Here are some alternatives.

Like death and taxes, buggy code is an unfortunate fact of life. Nearly every program ships with known bugs, and probably all of them end up with bugs that are discovered only post-deployment. There are many reasons for this sad state of affairs.

Software Transactional Memory: Why Is It Only a Research Toy?:
The promise of STM may likely be undermined by its overheads and workload applicabilities.

TM (transactional memory) is a concurrency control paradigm that provides atomic and isolated execution for regions of code. TM is considered by many researchers to be one of the most promising solutions to address the problem of programming multicore processors. Its most appealing feature is that most programmers only need to reason locally about shared data accesses, mark the code region to be executed transactionally, and let the underlying system ensure the correct concurrent execution. This model promises to provide the scalability of fine-grain locking, while avoiding common pitfalls of lock composition such as deadlock.

Software and the Concurrency Revolution:
Leveraging the full power of multicore processors demands new tools and new thinking from the software industry.

Concurrency has long been touted as the "next big thing" and "the way of the future," but for the past 30 years, mainstream software development has been able to ignore it. Our parallel future has finally arrived: new machines will be parallel machines, and this will require major changes in the way we develop software. The introductory article in this issue describes the hardware imperatives behind this shift in computer architecture from uniprocessors to multicore processors, also known as CMPs.

Spam, Spam, Spam, Spam, Spam, the FTC, and Spam:
A forum sponsored by the FTC highlights just how bad spam is, and how it’s only going to get worse without some intervention.

The Federal Trade Commission held a forum on spam in Washington, D.C., April 30 to May 2. Rather to my surprise, it was a really good, content-full event. The FTC folks had done their homework and had assembled panelists that ran the gamut from ardent anti-spammers all the way to hard-core spammers and everyone in between: lawyers, legitimate marketers, and representatives from vendor groups.

Spicing Up Dart with Side Effects:
A set of extensions to the Dart programming language, designed to support asynchrony and generator functions

The Dart programming language has recently incorporated a set of extensions designed to support asynchrony and generator functions. Because Dart is a language for Web programming, latency is an important concern. To avoid blocking, developers must make methods asynchronous when computing their results requires nontrivial time. Generator functions ease the task of computing iterable sequences.

Splinternet Behind the Great Firewall of China:
Once China opened its door to the world, it could not close it again.

What if you could not access YouTube, Facebook, Twitter, and Wikipedia? How would you feel if Google informed you that your connection had been reset during a search? What if Gmail was only periodically available, and Google Docs, which was used to compose this article, was completely unreachable? What a mess!

Standardizing Storage Clusters:
Will pNFS become the new standard for parallel data access?

Data-intensive applications such as data mining, movie animation, oil and gas exploration, and weather modeling generate and process huge amounts of data. File-data access throughput is critical for good performance. To scale well, these HPC (high-performance computing) applications distribute their computation among numerous client machines. HPC clusters can range from hundreds to thousands of clients with aggregate I/O demands ranging into the tens of gigabytes per second.

Static Analysis at GitHub:
An experience report

The Semantic Code team at GitHub builds and operates a suite of technologies that power symbolic code navigation on github.com. We learned that scale is about adoption, user behavior, incremental improvement, and utility. Static analysis in particular is difficult to scale with respect to human behavior; we often think of complex analysis tools working to find potentially problematic patterns in code and then trying to convince the humans to fix them.

Static Analysis: An Introduction:
The fundamental challenge of software engineering is one of complexity.

Modern static-analysis tools provide powerful and specific insights into codebases. The Linux kernel team, for example, developed Coccinelle, a powerful tool for searching, analyzing, and rewriting C source code; because the Linux kernel contains more than 27 million lines of code, a static-analysis tool is essential both for finding bugs and for making automated changes across its many libraries and modules. Another tool targeted at the C family of languages is Clang scan-build, which comes with many useful analyses and provides an API for programmers to write their own analyses. Like so many things in computer science, the utility of static analysis is self-referential: To write reliable programs, we must also write programs for our programs.

Statistics for Engineers:
Applying statistical techniques to operations data

Modern IT systems collect an increasing wealth of data from network gear, operating systems, applications, and other components. This data needs to be analyzed to derive vital information about the user experience and business performance. For instance, faults need to be detected, service quality needs to be measured and resource usage of the next days and month needs to be forecast.

Storage Systems: Not Just a Bunch of Disks Anymore:
The sheer size and scope of data available today puts tremendous pressure on storage systems to perform in ways never imagined.

The concept of a storage device has changed dramatically from the first magnetic disk drive introduced by the IBM RAMAC in 1956 to today’s server rooms with detached and fully networked storage servers. Storage has expanded in both large and small directions. All use the same underlying technology but they quickly diverge from there. Here we will focus on the larger storage systems that are typically detached from the server hosts. We will introduce the layers of protocols and translations that occur as bits make their way from the magnetic domains on the disk drives and interfaces to your desktop.

Storage Virtualization Gets Smart:
The days of overprovisioned, underutilized storage resources might soon become a thing of the past.

Over the past 20 years we have seen the transformation of storage from a dumb resource with fixed reliability, performance, and capacity to a much smarter resource that can actually play a role in how data is managed. In spite of the increasing capabilities of storage systems, however, traditional storage management models have made it hard to leverage these data management capabilities effectively. The net result has been overprovisioning and underutilization. In short, although the promise was that smart shared storage would simplify data management, the reality has been different.

Stream Processors: Progammability and Efficiency:
Will this new kid on the block muscle out ASIC and DSP?

Many signal processing applications require both efficiency and programmability. Baseband signal processing in 3G cellular base stations, for example, requires hundreds of GOPS (giga, or billions, of operations per second) with a power budget of a few watts, an efficiency of about 100 GOPS/W (GOPS per watt), or 10 pJ/op (picoJoules per operation). At the same time programmability is needed to follow evolving standards, to support multiple air interfaces, and to dynamically provision processing resources over different air interfaces. Digital television, surveillance video processing, automated optical inspection, and mobile cameras, camcorders, and 3G cellular handsets have similar needs.

Streams and Standards: Delivering Mobile Video:
The era of video served up to mobile phones has arrived and threatens to be the next “killer app” after wireless calling itself.

Don’t believe me? Follow along… Mobile phones are everywhere. Everybody has one. Think about the last time you were on an airplane and the flight was delayed on the ground. Immediately after the dreaded announcement, you heard everyone reach for their phones and start dialing.

Structured Deferral: Synchronization via Procrastination:
We simply do not have a synchronization mechanism that can enforce mutual exclusion.

Developers often take a proactive approach to software design, especially those from cultures valuing industriousness over procrastination. Lazy approaches, however, have proven their value, with examples including reference counting, garbage collection, and lazy evaluation. This structured deferral takes the form of synchronization via procrastination, specifically reference counting, hazard pointers, and RCU (read-copy-update).

Successful Strategies for IPv6 Rollouts. Really.:
Knowing where to begin is half the battle.

The design of TCP/IP began in 1973 when Robert Kahn and I started to explore the ramifications of interconnecting different kinds of packet-switched networks. We published a concept paper in May 1974, and a fairly complete specification for TCP was published in December 1974. By the end of 1975, several implementations had been completed and many problems were identified. Iteration began, and by 1977 it was concluded that TCP (by now called Transmission Control Protocol) should be split into two protocols: a simple Internet Protocol that carried datagrams end to end through packet networks interconnected through gateways; and a TCP that managed the flow and sequencing of packets exchanged between hosts on the contemplated Internet.

Surviving Software Dependencies:
Software reuse is finally here but comes with risks.

Software reuse is finally here, and its benefits should not be understated, but we’ve accepted this transformation without completely thinking through the potential consequences. The Copay and Equifax attacks are clear warnings of real problems in the way software dependencies are consumed today. There’s a lot of good software out there. Let’s work together to find out how to reuse it safely.

System Administration Soft Skills:
How can system administrators reduce stress and conflict in the workplace?

System administration can be both stressful and rewarding. Stress generally comes from outside factors such as conflict between SAs (system administrators) and their colleagues, a lack of resources, a high-interrupt environment, conflicting priorities, and SAs being held responsible for failures outside their control. What can SAs and their managers do to alleviate the stress? There are some well-known interpersonal and time-management techniques that can help, but these can be forgotten in times of crisis or just through force of habit.

TCP Offload to the Rescue:
Getting a toehold on TCP offload engines—and why we need them

In recent years, TCP/IP offload engines, known as TOEs, have attracted a good deal of industry attention and a sizable share of venture capital dollars. A TOE is a specialized network device that implements a significant portion of the TCP/IP protocol in hardware, thereby offloading TCP/IP processing from software running on a general-purpose CPU. This article examines the reasons behind the interest in TOEs and looks at challenges involved in their implementation and deployment.

Tackling Architectural Complexity with Modeling:
Component models can help diagnose architectural problems in both new and existing systems.

The ever-increasing might of modern computers has made it possible to solve problems once thought too difficult to tackle. Far too often, however, the systems for these functionally complex problem spaces have overly complicated architectures. In this article I use the term architecture to refer to the overall macro design of a system rather than the details of how the individual parts are implemented. The system architecture is what is behind the scenes of usable functionality, including internal and external communication mechanisms, component boundaries and coupling, and how the system will make use of any underlying infrastructure (databases, networks, etc.) .

Tear Down the Method Prisons! Set Free the Practices!:
Essence: a new way of thinking that promises to liberate the practices and enable true learning organizations

This article explains why we need to break out of this repetitive dysfunctional behavior, and it introduces Essence, a new way of thinking that promises to free the practices from their method prisons and thus enable true learning organizations.

Testable System Administration:
Models of indeterminism are changing IT management.

The methods of system administration have changed little in the past 20 years. While core IT technologies have improved in a multitude of ways, for many if not most organizations system administration is still based on production-line build logistics (aka provisioning) and reactive incident handling. As we progress into an information age, humans will need to work less like the machines they use and embrace knowledge-based approaches. That means exploiting simple (hands-free) automation that leaves us unencumbered to discover patterns and make decisions.

Testing a Distributed System:
Testing a distributed system can be trying even under the best of circumstances.

Distributed systems can be especially difficult to program, for a variety of reasons. They can be difficult to design, difficult to manage, and, above all, difficult to test. Testing a normal system can be trying even under the best of circumstances, and no matter how diligent the tester is, bugs can still get through. Now take all of the standard issues and multiply them by multiple processes written in multiple languages running on multiple boxes that could potentially all be on different operating systems, and there is potential for a real disaster.

The (not so) Hidden Computer:
The growing complexity of purpose-built systems is making it difficult to conceal the computers within.

Ubiquitous computing may not have arrived yet, but ubiquitous computers certainly have. The sustained improvements wrought by the fulfillment of Moore’s law have led to the use of microprocessors in a vast array of consumer products. A typical car contains 50 to 100 processors. Your microwave has one or maybe more. They’re in your TV, your phone, your refrigerator, your kids’ toys, and in some cases, your toothbrush.

The API Performance Contract:
How can the expected interactions between caller and implementation be guaranteed?

When you call functions in an API, you expect them to work correctly; sometimes this expectation is called a contract between the caller and the implementation. Callers also have performance expectations about these functions, and often the success of a software system depends on the API meeting these expectations. So there’s a performance contract as well as a correctness contract. The performance contract is usually implicit, often vague, and sometimes breached (by caller or implementation). How can this aspect of API design and documentation be improved?

The Age of Corporate Open Source Enlightenment:
Like it or not, zealots and heretics are finding common ground in the open source holy war.

It’s a bad idea, mixing politics and religion. Conventional wisdom tells us to keep them separate - and to discuss neither at a dinner party. The same has been said about the world of software. When it comes to mixing the open source church with the proprietary state (or is it the other way around?), only one rule applies: Don’t do it.

The Answer is 42 of Course:
If we want our networks to be sufficiently difficult to penetrate, we’ve got to ask the right questions.

Why is security so hard? As a security consultant, I’m glad that people feel that way, because that perception pays my mortgage. But is it really so difficult to build systems that are impenetrable to the bad guys?

The Antifragile Organization:
Embracing Failure to Improve Resilience and Maximize Availability

Failure is inevitable. Disks fail. Software bugs lie dormant waiting for just the right conditions to bite. People make mistakes. Data centers are built on farms of unreliable commodity hardware. If you’re running in a cloud environment, then many of these factors are outside of your control. To compound the problem, failure is not predictable and doesn’t occur with uniform probability and frequency. The lack of a uniform frequency increases uncertainty and risk in the system.

The Balancing Act of Choosing Nonblocking Features:
Design requirements of nonblocking systems

What is nonblocking progress? Consider the simple example of incrementing a counter C shared among multiple threads. One way to do so is by protecting the steps of incrementing C by a mutual exclusion lock L (i.e., acquire(L); old := C ; C := old+1; release(L);). If a thread P is holding L, then a different thread Q must wait for P to release L before Q can proceed to operate on C. That is, Q is blocked by P.

The Big Bang Theory of IDEs:
Pondering the vastness of the ever-expanding universe of IDEs, you might wonder whether a usable IDE is too much to ask for.

Remember the halcyon days when development required only a text editor, a compiler, and some sort of debugger (in cases where the odd printf() or two alone didn’t serve)? During the early days of computing, these were independent tools used iteratively in development’s golden circle. Somewhere along the way we realized that a closer integration of these tools could expedite the development process. Thus was born the integrated development environment (IDE), a framework and user environment for software development that’s actually a toolkit of instruments essential to software creation. At first, IDEs simply connected the big three (editor, compiler, and debugger), but nowadays most go well beyond those minimum requirements.

The Calculus of Service Availability:
You’re only as available as the sum of your dependencies.

Most services offered by Google aim to offer 99.99 percent (sometimes referred to as the "four 9s") availability to users. Some services contractually commit to a lower figure externally but set a 99.99 percent target internally. This more stringent target accounts for situations in which users become unhappy with service performance well before a contract violation occurs, as the number one aim of an SRE team is to keep users happy. For many services, a 99.99 percent internal target represents the sweet spot that balances cost, complexity, and availability.

The Case Against Data Lock-in:
Want to keep your users? Just make it easy for them to leave.

Engineers employ many different tactics to focus on the user when writing software: for example, listening to user feedback, fixing bugs, and adding features that their users are clamoring for. Since Web-based services have made it easier for users to move to new applications, it’s becoming even more important to focus on building and retaining user trust. We’ve found that an incredibly effective way to earn and maintain user trust is to make it easy for users to leave your product with their data in tow. This not only prevents lock-in and engenders trust, but also forces your team to innovate and compete on technical merit.

The Challenge of Cross-language Interoperability:
Interfacing between languages is increasingly important.

Interoperability between languages has been a problem since the second programming language was invented. Solutions have ranged from language-independent object models such as COM (Component Object Model) and CORBA (Common Object Request Broker Architecture) to VMs (virtual machines) designed to integrate languages, such as JVM (Java Virtual Machine) and CLR (Common Language Runtime). With software becoming ever more complex and hardware less homogeneous, the likelihood of a single language being the correct tool for an entire program is lower than ever. As modern compilers become more modular, there is potential for a new generation of interesting solutions.

The Complex Path to Quantum Resistance:
Is your organization prepared?

There is a new technology on the horizon that will forever change the information security and privacy industry landscape. Quantum computing, together with quantum communication, will have many beneficial applications but will also be capable of breaking many of today's most popular cryptographic techniques that help ensure data protection?in particular, confidentiality and integrity of sensitive information. These techniques are ubiquitously embedded in today's digital fabric and implemented by many industries such as finance, health care, utilities, and the broader information communication technology (ICT) community.

The Cost of Virtualization:
Software developers need to be aware of the compromises they face when using virtualization technology.

Virtualization can be implemented in many different ways. It can be done with and without hardware support. The virtualized operating system can be expected to be changed in preparation for virtualization, or it can be expected to work unchanged. Regardless, software developers must strive to meet the three goals of virtualization spelled out by Gerald Popek and Robert Goldberg: fidelity, performance, and safety.

The Curse of the Excluded Middle:
Mostly functional programming does not work.

There is a trend in the software industry to sell "mostly functional" programming as the silver bullet for solving problems developers face with concurrency, parallelism (manycore), and, of course, Big Data. Contemporary imperative languages could continue the ongoing trend, embrace closures, and try to limit mutation and other side effects. Unfortunately, just as "mostly secure" does not work, "mostly functional" does not work either. Instead, developers should seriously consider a completely fundamentalist option as well: embrace pure lazy functional programming with all effects explicitly surfaced in the type system using monads.

The Debugging Mindset:
Understanding the psychology of learning strategies leads to effective problem-solving skills.

Software developers spend 35-50 percent of their time validating and debugging software. The cost of debugging, testing, and verification is estimated to account for 50-75 percent of the total budget of software development projects, amounting to more than $100 billion annually. While tools, languages, and environments have reduced the time spent on individual debugging tasks, they have not significantly reduced the total time spent debugging, nor the cost of doing so. Therefore, a hyperfocus on elimination of bugs during development is counterproductive; programmers should instead embrace debugging as an exercise in problem solving.

The Deliberate Revolution:
Transforming Integration With XML Web Services

While detractors snub XML web services as CORBA with a weight problem, industry cheerleaders say these services are ushering in a new age of seamless integrated computing. But for those of us whose jobs don’t involve building industry excitement, what do web services offer?

The Die is Cast:
Hardware Security is Not Assured

The future of hardware security will evolve with hardware. As packaging advances and focus moves to beyond Moore's law technologies, hardware security experts will need to keep ahead of changing security paradigms, including system and process vulnerabilities. Research focused on quantum hacking is emblematic of the translation of principles of security on the physical attack plane for emerging communications and computing technologies. Perhaps the commercial market will evolve such that the GAO will run a study on compromised quantum technologies in the not-too-distant future.

The Effects of Mixing Machine Learning and Human Judgment:
Collaboration between humans and machines does not necessarily lead to better outcomes.

Based on the theoretical findings from the existing literature, some policymakers and software engineers contend that algorithmic risk assessments such as the COMPAS software can alleviate the incarceration epidemic and the occurrence of violent crimes by informing and improving decisions about policing, treatment, and sentencing. Considered in tandem, these findings indicate that collaboration between humans and machines does not necessarily lead to better outcomes, and human supervision does not sufficiently address problems when algorithms err or demonstrate concerning biases.

The Emergence of iSCSI:
Modern SCSI, as defined by the SCSI-3 Architecture Model, or SAM, really considers the cable and physical interconnections to storage as only one level in a larger hierarchy.

When most IT pros think of SCSI, images of fat cables with many fragile pins come to mind. Certainly, that’s one manifestation. But modern SCSI, as defined by the SCSI-3 Architecture Model, or SAM, really considers the cable and physical interconnections to storage as only one level in a larger hierarchy. By separating the instructions or commands sent to and from devices from the physical layers and their protocols, you arrive at a more generic approach to storage communication

The Essence of Software Engineering: The SEMAT Kernel:
A thinking framework in the form of an actionable kernel

Everyone who develops software knows that it is a complex and risky business, and its participants are always on the lookout for new ideas that will lead to better software. Fortunately, software engineering is still a young and growing profession that sees innovations and improvements in best practices every year. Just look, for example, at the improvements and benefits that lean and agile thinking have brought to software-development teams.

The Evolution of Security:
What can nature tell us about how best to manage our risks?

Security people are never in charge unless an acute embarrassment has occurred. Otherwise, their advice is tempered by “economic reality,” which is to say that security is a means, not an end. This is as it should be. Since means are about tradeoffs, security is about trade-offs, but you knew all that. Our tradeoff decisions can be hard to make, and these hard-to-make decisions come in two varieties. One type occurs when the uncertainty of the alternatives is so great that they can’t be sorted in terms of probable effect. As such, other factors such as familiarity or convenience will drive the decision.

The Evolution of Web Development for Mobile Devices:
Building Web sites that perform well on mobile devices remains a challenge.

The biggest change in Web development over the past few years has been the remarkable rise of mobile computing. Mobile phones used to be extremely limited devices that were best used for making phone calls and sending short text messages. Today’s mobile phones are more powerful than the computers that took Apollo 11 to the moon with the ability to send data to and from nearly anywhere.

The Family Dynamics of 802.11:
The 802.11 family of standards is helping to move wireless LANs into promising new territory.

Three trends are driving the rapid growth of wireless LAN (WLAN): The increased use of laptops and personal digital assistants (PDAs); rapid advances in WLAN data rates (from 2 megabits per second to 108 Mbps in the past four years); and precipitous drops in WLAN prices (currently under $50 for a client and under $100 for an access point).

The Five-Minute Rule 20 Years Later: and How Flash Memory Changes the Rules:
The old rule continues to evolve, while flash memory adds two new rules.

In 1987, Jim Gray and Gianfranco Putzolu published their now-famous five-minute rule for trading off memory and I/O capacity. Their calculation compares the cost of holding a record (or page) permanently in memory with the cost of performing disk I/O each time the record (or page) is accessed, using appropriate fractions of prices for RAM chips and disk drives. The name of their rule refers to the break-even interval between accesses. If a record (or page) is accessed more often, it should be kept in memory; otherwise, it should remain on disk and read when needed.

The Flame Graph:
This visualization of software execution is a new necessity for performance profiling and debugging.

An everyday problem in our industry is understanding how software is consuming resources, particularly CPUs. What exactly is consuming how much, and how did this change since the last software version? These questions can be answered using software profilers, tools that help direct developers to optimize their code and operators to tune their environment. The output of profilers can be verbose, however, making it laborious to study and comprehend. The flame graph provides a new visualization for profiler output and can make for much faster comprehension, reducing the time for root cause analysis.

The Future of Human-Computer Interaction:
Is an HCI revolution just around the corner?

Personal computing launched with the IBM PC. But popular computing—computing for the masses—launched with the modern WIMP (windows, icons, mouse, pointer) interface, which made computers usable by ordinary people. As popular computing has grown, the role of HCI (human-computer interaction) has increased. Most software today is interactive, and code related to the interface is more than half of all code. HCI also has a key role in application design. In a consumer market, a product’s success depends on each user’s experience with it.

The Future of Microprocessors:
Chip multiprocessors’ promise of huge performance gains is now a reality.

The performance of microprocessors that power modern computers has continued to increase exponentially over the years for two main reasons. First, the transistors that are the heart of the circuits in all processors and memory chips have simply become faster over time on a course described by Moore’s law, and this directly affects the performance of processors built with those transistors. Moreover, actual processor performance has increased faster than Moore’s law would predict, because processor designers have been able to harness the increasing numbers of transistors available on modern chips to extract more parallelism from software.

The Future of WLAN:
Overcoming the Top Ten Challenges in wireless networking--will it allow wide-area mesh networks to become ubiquitous?

Since James Clerk Maxwell first mathematically described electromagnetic waves almost a century and a half ago, the world has seen steady progress toward using them in better and more varied ways. Voice has been the killer application for wireless for the past century. As performance in all areas of engineering has improved, wireless voice has migrated from a mass broadcast medium to a peer-to-peer medium. The ability to talk to anyone on the planet from anywhere on the planet has fundamentally altered the way society works and the speed with which it changes.

The Heart of Eclipse:
A look inside an extensible plug-in architecture

ECLIPSE is both an open, extensible development environment for building software and an open, extensible application framework upon which software can be built. Considered the most popular Java IDE, it provides a common UI model for working with tools and promotes rapid development of modular features based on a plug-in component model. The Eclipse Foundation designed the platform to run natively on multiple operating systems, including Macintosh, Windows, and Linux, providing robust integration with each and providing rich clients that support the GUI interactions everyone is familiar with: drag and drop, cut and paste (clipboard), navigation, and customization.

The Hidden Dividends of Microservices:
Microservices aren’t for every company, and the journey isn’t easy.

Microservices are an approach to building distributed systems in which services are exposed only through hardened APIs; the services themselves have a high degree of internal cohesion around a specific and well-bounded context or area of responsibility, and the coupling between them is loose. Such services are typically simple, yet they can be composed into very rich and elaborate applications. The effort required to adopt a microservices-based approach is considerable, particularly in cases that involve migration from more monolithic architectures. The explicit benefits of microservices are well known and numerous, however, and can include increased agility, resilience, scalability, and developer productivity.

The History, Status, and Future of FPGAs:
Hitting a nerve with field-programmable gate arrays

This article is a summary of a three-hour discussion at Stanford University in September 2019 among the authors. It has been written with combined experiences at and with organizations such as Zilog, Altera, Xilinx, Achronix, Intel, IBM, Stanford, MIT, Berkeley, University of Wisconsin, the Technion, Fairchild, Bell Labs, Bigstream, Google, DIGITAL (DEC), SUN, Nokia, SRI, Hitachi, Silicom, Maxeler Technologies, VMware, Xerox PARC, Cisco, and many others. These organizations are not responsible for the content, but may have inspired the authors in some ways, to arrive at the colorful ride through FPGA space described above.

The Hitchhiker’s Guide to Biomorphic Software:
The natural world may be the inspiration we need for solving our computer problems.

The natural world may be the inspiration we need for solving our computer problems. While it is certainly true that "the map is not the territory," most visitors to a foreign country do prefer to take with them at least a guidebook to help locate themselves as they begin their explorations. That is the intent of this article. Although there will not be enough time to visit all the major tourist sites, with a little effort and using the information in the article as signposts, the intrepid explorer can easily find numerous other, interesting paths to explore.

The IDAR Graph:
An improvement over UML

UML is the de facto standard for representing object-oriented designs. It does a fine job of recording designs, but it has a severe problem: its diagrams don’t convey what humans need to know, making them hard to understand. This is why most software developers use UML only when forced to. People understand an organization, such as a corporation, in terms of a control hierarchy. When faced with an organization of people or objects, the first question usually is, "What’s controlling all this?" Surprisingly, UML has no concept of one object controlling another. Consequently, in every type of UML diagram, no object appears to have greater or lesser control than its neighbors.

The Ideal HPC Programming Language:
Maybe it’s Fortran. Or maybe it just doesn’t matter.

The DARPA HPCS program sought a tenfold productivity improvement in trans-petaflop systems for HPC. This article describes programmability studies undertaken by Sun Microsystems in its HPCS participation. These studies were distinct from Sun’s ongoing development of a new HPC programming language (Fortress) and the company’s broader HPCS productivity studies, though there was certainly overlap with both activities.

The Identity in Everyone's Pocket:
Keeping users secure through their smartphones

Newer phones use security features in many different ways and combinations. As with any security technology, however, using a feature incorrectly can create a false sense of security. As such, many app developers and service providers today do not use any of the secure identity-management facilities that modern phones offer. For those of you who fall into this camp, this article is meant to leave you with ideas about how to bring a hardware-backed and biometrics-based concept of user identity into your ecosystem.

The Inevitability of Reconfigurable Systems:
The transition from instruction-based to reconfigurable circuits will not be easy, but has its time come?

The introduction of the microprocessor in 1971 marked the beginning of a 30-year stall in design methods for electronic systems. The industry is coming out of the stall by shifting from programmed to reconfigurable systems. In programmed systems, a linear sequence of configuration bits, organized into blocks called instructions, configures fixed hardware to mimic custom hardware. In reconfigurable systems, the physical connections among logic elements change with time to mimic custom hardware. The transition to reconfigurable systems will be wrenching, but this is inevitable as the design emphasis shifts from cost performance to cost performance per watt. Here’s the story.

The Insider, Naivety, and Hostility: Security Perfect Storm?:
Keeping nasties out if only half the battle.

Every year corporations and government installations spend millions of dollars fortifying their network infrastructures. Firewalls, intrusion detection systems, and antivirus products stand guard at network boundaries, and individuals monitor countless logs and sensors for even the subtlest hints of network penetration. Vendors and IT managers have focused on keeping the wily hacker outside the network perimeter, but very few technological measures exist to guard against insiders - those entities that operate inside the fortified network boundary. The 2002 CSI/FBI survey estimates that 70 percent of successful attacks come from the inside. Several other estimates place those numbers even higher.

The Invisible Assistant:
One lab’s experiment with ubiquitous computing

Ubiquitous computing seeks to place computers everywhere around us—into the very fabric of everyday life1—so that our lives are made better. Whether it is improving our job productivity, our ability to stay connected with family and friends, or our entertainment, the goal is to find ways to put technology to work for us by getting all those computers—large and small, visible and invisible—to work together.

The Long Road to 64 Bits:
Double, double, toil and trouble

Shakespeare’s words often cover circumstances beyond his wildest dreams. Toil and trouble accompany major computing transitions, even when people plan ahead. To calibrate “tomorrow’s legacy today,” we should study “tomorrow’s legacy yesterday.” Much of tomorrow’s software will still be driven by decades-old decisions. Past decisions have unanticipated side effects that last decades and can be difficult to undo.

The Magic of RFID:
Just how do those little things work anyway?

Many modern technologies give the impression they work by magic, particularly when they operate automatically and their mechanisms are invisible. A technology called RFID (radio frequency identification), which is relatively new to the mass market, has exactly this characteristic and for many people seems a lot like magic. RFID is an electronic tagging technology that allows an object, place, or person to be automatically identified at a distance without a direct line-of-sight, using an electromagnetic challenge/response exchange.

The Mythos of Model Interpretability:
In machine learning, the concept of interpretability is both important and slippery.

Supervised machine-learning models boast remarkable predictive capabilities. But can you trust your model? Will it work in deployment? What else can it tell you about the world?

The NSA and Snowden: Securing the All-Seeing Eye:
How good security at the NSA could have stopped him

Edward Snowden, while an NSA (National Security Agency) contractor at Booz Allen Hamilton in Hawaii, copied up to 1.7 million top-secret and above documents, smuggling copies on a thumb drive out of the secure facility in which he worked, and later released many to the press. This has altered the relationship of the U.S. government with the American people, as well as with other countries. This article examines the computer security aspects of how the NSA could have prevented this, perhaps the most damaging breach of secrets in U.S. history.

The Network is Reliable:
An informal survey of real-world communications failures

The network is reliable tops Peter Deutsch’s classic list, "Eight fallacies of distributed computing", "all [of which] prove to be false in the long run and all [of which] cause big trouble and painful learning experiences." Accounting for and understanding the implications of network behavior is key to designing robust distributed programs; in fact, six of Deutsch’s "fallacies" directly pertain to limitations on networked communications.

The Network’s New Role:
Application-oriented networks can help bridge the gap between enterprises.

Companies have always been challenged with integrating systems across organizational boundaries. With the advent of Internet-native systems, this integration has become essential for modern organizations, but it has also become more and more complex, especially as next-generation business systems depend on agile, flexible, interoperable, reliable, and secure cross-enterprise systems.

The Obama Campaign:
The Obama campaign has been praised for its innovative use of technology. What was the key to its success?

On January 3, 2008, I sat in the boiler room waiting for the caucus to commence. At 7 p.m. the doors had been open for about an hour: months of preparation were coming to fruition. The phone calls had been made, volunteers had been canvassing, and now the moment had come. Could Barack Obama win the Iowa caucus? Doors closed and the first text message came from a precinct: it looked like a large attendance. Then came the second, the third, the fourth. Each was typed into our model, and a projection was starting to form. The fifth, the sixth, and now the seventh.

The Pain of Implementing LINQ Providers:
It’s no easy task for NoSQL

I remember sitting on the edge of my seat watching the 2005 PDC (Professional Developers Conference) videos that first showed LINQ (Language Integrated Query). I wanted LINQ: it offered just about everything that I could hope for to make working with data easy. The impetus for building queries into the language is quite simple; it is something that is used all the time; and the promise of a unified querying model is good enough, even before you add all the language goodies that were dropped on us. Being able to write in C# and have the database magically understand what I am doing?

The Pathologies of Big Data:
Scale up your datasets enough and all your apps will come undone. What are the typical problems and where do the bottlenecks generally surface?

What is "big data" anyway? Gigabytes? Terabytes? Petabytes? A brief personal memory may provide some perspective. In the late 1980s at Columbia University I had the chance to play around with what at the time was a truly enormous "disk": the IBM 3850 MSS (Mass Storage System). The MSS was actually a fully automatic robotic tape library and associated staging disks to make random access, if not exactly instantaneous, at least fully transparent. In Columbia’s configuration, it stored a total of around 100 GB. It was already on its way out by the time I got my hands on it, but in its heyday, the early to mid-1980s, it had been used to support access by social scientists to what was unquestionably "big data" at the time: the entire 1980 U.S.

The Price of Performance:
An Economic Case for Chip Multiprocessing

In the late 1990s, our research group at DEC was one of a growing number of teams advocating the CMP (chip multiprocessor) as an alternative to highly complex single-threaded CPUs. We were designing the Piranha system,1 which was a radical point in the CMP design space in that we used very simple cores (similar to the early RISC designs of the late ’80s) to provide a higher level of thread-level parallelism. Our main goal was to achieve the best commercial workload performance for a given silicon budget. Today, in developing Google’s computing infrastructure, our focus is broader than performance alone. The merits of a particular architecture are measured by answering the following question: Are you able to afford the computational capacity you need?

The Reincarnation of Virtual Machines:
Virtualization makes a comeback.

The term virtual machine initially described a 1960s operating system concept: a software abstraction with the looks of a computer system’s hardware (real machine). Forty years later, the term encompasses a large range of abstractions?for example, Java virtual machines that don’t match an existing real machine. Despite the variations, in all definitions the virtual machine is a target for a programmer or compilation system. In other words, software is written to run on the virtual machine.

The Reliability of Enterprise Applications:
Understanding enterprise reliability

Enterprise reliability is a discipline that ensures applications will deliver the required business functionality in a consistent, predictable, and cost-effective manner without compromising core aspects such as availability, performance, and maintainability. This article describes a core set of principles and engineering methodologies that enterprises can apply to help them navigate the complex environment of enterprise reliability and deliver highly reliable and cost-efficient applications.

The Responsive Enterprise: Embracing the Hacker Way:
Soon every company will be a software company.