Dependability [reliability]

Dependability can be defined by maintenance costs and how long the maintenance takes. It also can be defined in terms of continuous operation. Finally, it can be defined by how well it endures abuse or failure. The following terms help define and quantify dependability: reliability, fault tolerance or performability, maintainability, testability, availability and safety.     

Why software fails [software failure]

Most IT experts agree that software failures occur far more often than they should despite the fact that, for the most part, they are predictable and avoidable. It is unfortunate that most organizations don't see preventing failure as an urgent matter, even though that view risks harming the organization and maybe even destroying it. Because software failure has tremendous implications for business and society, it is important to understand why this attitude persists.     

Semantic failure [of software]

The author offers the opinion that the adoption of the terminology of hardware reliability in the context of software was a terrible, probably unavoidable, and perhaps even necessary, mistake: terrible-because the words cannot have the same meanings in both contexts; and unavoidable-because today there are few systems whose reliability can be assessed without dealing with both     

The exterminators [software bugs]

This paper describes a sound methodology developed at Praxis High Integrity Systems for detecting and exterminating bugs during all stages of a software project. To develop software, the London-based software house uses mathematically based techniques, known as formal methods, which require that programmers begin their work not by writing code but rather by stringing together special symbols that represent the program's logic. Like a mathematical theorem, these symbol strings can be checked to verify that they form logically correct statements. Once the programmer has checked that the program doesn't have logical flaws, it's a relatively simple matter to convert those symbols into programming code. With an average of less than one error in every 10,000 lines of delivered code, Praxis claims a bug rate that is at least 50 times better than the industry standard.     

Crashproof codes [flight software]

Boeing Co. and NASA have joined forces for the Active Aeroelastic Wing (AAW) Project to test the way a modified F/A-18 strike fighter uses its wings. The AAW was designed to be flexible enough to be twisted on demand in flight and it could herald nothing less than a revolution in aviation. The twisting can be used to control the plane's roll, reducing and ultimately eliminating the need for ailerons and flaps and their associated hardware. AAW-equipped planes would result to increased fuel efficiency and improved maneuverability, able to execute sharper turns at higher speeds. A special flight software was developed to keep track of the plane's speed, altitude, and attitude while monitoring the pilot's controls for commands. Based on a set of rules known as control laws, the software must then translate any commands from the pilot into movements of the aircraft's various control surfaces such as the rudders or, most significantly, the flaps that flex the AAWs. Despite its complex and critical job, the flight software is compact, consisting of only about 13,000 lines of source code written in the Ada language.     

Collaboration nation [group software]

As group software assumes a major role in the workplace, will engineers stop talking to each other? Communication is the essence of collaboration, and increasingly communication about semiconductor design is happening over the Internet not only through e-mail and threaded discussion boards, but also through specially designed Web collaboration software that lets engineers work on parts of the same chip simultaneously, whether they are down the hall or across the world. The increasing use of collaborative software has raised concerns that the engineering workplace would suffer from diminished human contact, and that engineers would be transformed into zombie-like automatons, addicted to their workstations. That hasn't happened; workplace experts say that engineers rely as much as ever on face-to-face interactions.     

Performability of the hypercube [reliability]

The authors address the problem of modeling and evaluating the composite performance and reliability measures (performability) of a hypercube architecture running a specific application. A generalized stochastic Petri net (GSPN) is used to model the component failures and repairs in the hypercube. The GSPN model defines the dimension and number of subcubes available for the application. This model generalizes previously proposed models for hypercube reliability and automatically generates the underlying Markov chain needed for performability analysis. A novel performability analysis algorithm is presented that computes both the moments and the distribution of performability in O( N³). The algorithm is conceptually simpler than those previously reported. An example is given to illustrate the modeling process and demonstrate the importance of performability analysis for mission-critical systems     

Total recall [life recording software]

This paper describes a Microsoft research initiative that focuses on memory augmentation. The research is primarily based on the MyLifeBits Project of Microsoft researcher, Gordon Bell, who, for two years, collected real life data using sensors and a still camera, called SenseCam, with the aim of developing a improved means of information retrieval. With the MyLifeBits software, the SenseCam, and the low cost of memory of all kinds, the rebirth of the PC into a personal mainframe can be realized.     

Modified `practical Bayes-estimators' [reliability theory]

This paper presents a new formulation of `practical Bayes-estimators' (PBE) for the 2-parameter Weibull model when both parameters are unknown. Overcoming some limitations of the first formulation gave rise to this work, but the results are beyond this intent. These estimators are a tool to improve technical knowledge by using a few experimental data. In this case, the controversy about whether to use Bayes or classical methods is surmounted since estimators, like maximum likelihood, give estimates that often appear unlikely on the basis of technical knowledge of the engineers. A Monte Carlo study supports the following conclusions: if the shape parameter is greater than one, modified PBE maintain the good properties of practical Bayes estimators; otherwise the modified PBE are much better and do not suffer from the past limitation regarding the formulation of the prior interval on the shape parameter itself; and when there are very few data the modified PBE work as a filter that always improves (on average) the prior information if it is poor, or substantially confirms it if it is good. From this viewpoint, Bayes theorem allows statistics to help engineering and not vice versa     

Open-source media [mobile multimedia software]

Multimedia is opening up a vast new frontier for software companies, thanks to the rapid growth of broadband connections to desktop computers and ever more capable cell-phones and wireless PDAs. RealNetworks is about to find out if its open-source gambit is going to pay off, as the first wave of Helix-powered hardware reaches the market. So far, only a handful of such devices have been released, including the Sony Vega television in Japan and the palmOne Treo 650 smart phone in the United States. No doubt other software vendors are watching closely; an open-source model that compels all developers to assign copyright back to the "mother ship" could soon become the preferred way to nurture communities of developers.     

A Gibbs-sampler approach to estimate the number of faults in asystem using capture-recapture sampling [software reliability]

A new recapture debugging model is suggested to estimate the number of faults in a system, ν, and the failure intensity of each fault, φ. The Gibbs sampler and the Metropolis algorithm are used in this inference procedure. A numerical illustration suggests a notable improvement on the estimation of ν and φ compared with that of a removal debugging model     

Modelling an imperfect debugging phenomenon in software reliability

Several Software Reliability Growth Models (SRGMs) have been developed in the literature assuming the debugging process to be perfect and thus implying that there is one-to-one correspondence between the number of failures observed and errors removed. However, in reality it is possible that the error which is supposed to have been removed may cause a failure again. It may be due to the spawning of a new error because of imperfect debugging. If such a phenomenon exists then the Software Reliability Growth is S-shaped. In this paper, we develop a model which can describe imperfect debugging process and has the inbuilt flexibility of capturing a wide class of growth curves. Earlier attempts of modelling such a process were able to capture only a particular curve. In other words, if a failure observation phenomenon is exponential then the error removal is again modelled by an exponential growth curve. Applicability of the model has been shown on several data sets obtained from different software development projects.     

Quality enhances reliability [power supplies]

As deregulation dawns, electric utilities are awakening to the fact that power quality counts with many a customer-and counts for a lot. Even now, the groundwork is being laid worldwide for a new type of service contract between a utility and its large industrial or commercial clients. In brief, the utility promises to supply its customer's operations with power above a certain level of “quality”, and the customer promises to buy power from no-one else for as long as the contract lasts-a valuable concession now that retail wheeling has clients in those categories picking and choosing among suppliers in the electric power industry     

The African hacker [software development]

This paper narrates the success story of Hermann Chinery-Hesse, chief of Soft Tribe Ltd. located at Ghana, West Africa. Chinery-Hesse has made a small fortune writing software, working as a systems architect, and selling computer code to hundreds of businesses in his country. Through Soft, Chinery-Hesse has also been providing training programs for the country's growing population of full-time programmers. His dream remains to expand software in Ghana, to make more money and to show the world that despite the often depressing headlines about poverty and mayhem in Africa, there are opportunities for technical talent.     

Beating the heat [CMOS hot-carrier reliability]

CMOS hot-carrier reliability at both transistor and circuit levels has been examined. Accurate reliability assessment requires defining suitable criteria for acceptable performance for both circuit and individual transistors. As device designers meet demands for greater speed and more complex circuitry accompanied by shrinking the size of transistor into the deep-submicron regime, they have to contend with increase in current densities and higher electric fields. Though in general a MOSFET's driving capability increases as the channel length decreases, the resulting high field will eventually limit the driving capability of the device. The authors discuss improving CMOS hot-carrier reliability through analysis, modelling and simulation     

Automatic test-generation for predicates [software testing]

The authors propose a new technique for the automatic generation of test cases for predicates. Earlier, they proposed an efficient effective test generation strategy for Boolean expressions. They now extend this strategy to predicates. Their new strategy addresses several issues, including: analysis of dependencies between relational expressions in a predicate 𝒫; generation of test constraints for 𝒫 based on the detection of Boolean and relational operator faults in 𝒫; and generation of actual tests according to the generated test constraints for 𝒫. They propose: the use of constraint logic programming (CLP) to automate test-data generation for a predicate; and an incremental approach to apply CLP techniques to solve a constraint system. Since their technique is specification-based, it can facilitate generation of anticipated outputs for actual tests