Rigorously assessing software reliability and safety

This paper summarises the state of the art in the assessment of software reliability and safety ("dependability"), and describes some promising developments. A sound demonstration of very high dependability is still impossible before operation of the software; but research is finding ways to make rigorous assessment increasingly feasible. While refined mathematical techniques cannot take the place of factual knowledge, they can allow the decision-maker to draw more accurate conclusions from the knowledge that is available

Inefficiencies in markets for intellectual property rights: experiences of academic and public research institutions

The formal use of such intellectual property rights (IPR) as patents and registered copyright by universities has increased steadily in the last two decades. Mainstream arguments, embedded in economic theory and policy, advocating the use of IPR to protect academic research results are based on the view that IPR marketplaces work well and allow universities to reap significant benefits. However, there is a lack of evidence-based research to justify or critically evaluate these claims. Building upon an original survey of 46 universities and public research organizations in the United Kingdom, this study analyses the quality of the institutions underpinning the markets for patents and copyright, investigating potential inefficiencies that could lead to underperformance of the IPR system. These include ‘IPR market failures’ with respect to search processes and transparency; price negotiation processes; uncertainties in the perception of the economic value of IRP and the relationship with R&D cost. Further sources of underperformance may include ‘institutional failures’ with respect to enforcement and regulation. Particular attention is paid to the role of governance forms (e.g. alternative types of licensing agreements) through which IPR exchanges take place. We find that a high share of universities report market failures in IPR transactions and that the choice of IPR governance forms matter for the obstacles that are encountered. Given the importance of widely disseminating university research outcomes to foster innovation and economic development, the presence of inefficiencies in IPR markets suggests that such objectives could best be achieved by encouraging open distribution of knowledge, rather than privatization of academic knowledge

Assessing Asymmetric Fault-Tolerant Software

The most popular forms of fault tolerance against design faults use "asymmetric" architectures in which a "primary" part performs the computation and a "secondary" part is in charge of detecting errors and performing some kind of error processing and recovery. In contrast, the most studied forms of software fault tolerance are "symmetric" ones, e.g. N-version programming. The latter are often controversial, the former are not. We discuss how to assess the dependability gains achieved by these methods. Substantial difficulties have been shown to exist for symmetric schemes, but we show that the same difficulties affect asymmetric schemes. Indeed, the latter present somewhat subtler problems. In both cases, to predict the dependability of the fault-tolerant system it is not enough to know the dependability of the individual components. We extend to asymmetric architectures the style of probabilistic modeling that has been useful for describing the dependability of "symmetric" architectures, to highlight factors that complicate the assessment. In the light of these models, we finally discuss fault injection approaches to estimating coverage factors. We highlight the limits of what can be predicted and some useful research directions towards clarifying and extending the range of situations in which estimates of coverage of fault tolerance mechanisms can be trusted

Design diversity: an update from research on reliability modelling

Diversity between redundant subsystems is, in various forms, a common design approach for improving system dependability. Its value in the case of software-based systems is still controversial. This paper gives an overview of reliability modelling work we carried out in recent projects on design diversity, presented in the context of previous knowledge and practice. These results provide additional insight for decisions in applying diversity and in assessing diverseredundant systems. A general observation is that, just as diversity is a very general design approach, the models of diversity can help conceptual understanding of a range of different situations. We summarise results in the general modelling of common-mode failure, in inference from observed failure data, and in decision-making for diversity in development.

Software reliability and dependability: a roadmap

Shifting the focus from software reliability to user-centred measures of dependability in complete software-based systems. Influencing design practice to facilitate dependability assessment. Propagating awareness of dependability issues and the use of existing, useful methods. Injecting some rigour in the use of process-related evidence for dependability assessment. Better understanding issues of diversity and variation as drivers of dependability. Bev Littlewood is founder-Director of the Centre for Software Reliability, and Professor of Software Engineering at City University, London. Prof Littlewood has worked for many years on problems associated with the modelling and evaluation of the dependability of software-based systems; he has published many papers in international journals and conference proceedings and has edited several books. Much of this work has been carried out in collaborative projects, including the successful EC-funded projects SHIP, PDCS, PDCS2, DeVa. He has been employed as a consultant t

The trust preferred CDO market: from start to (expected) finish

This paper investigates the development, issuance, structuring, and expected performance of the trust preferred securities collateralized debt obligation (TruPS CDO) market. Developed as a way to provide capital markets access to smaller banks, thrifts, insurance companies, and real estate investment trusts (REITs) by pooling the issuance of TruPS into marketable CDOs, the market grew to $60 billion of issuance from its inception in 2000 through its abrupt halt in 2007. As evidenced by rating agency downgrades, current performance, and estimates from the authors' own model, TruPS CDOs are likely to perform poorly. Using data and valuation software from the leading provider of such information, they estimate that large numbers of the subordinated bonds and some senior bonds will be either fully or partially written down, even if no further defaults occur going forward. The primary reason for these losses is that the underlying collateral of TruPS CDOs is small, unrated banks whose primary asset is commercial real estate (CRE). During their years of greatest issuance from 2003 to 2007, the booming real estate market and record low number of bank failures masked the underlying risks that are now manifest. Another reason for the poor performance of bank TruPS CDOs is that smaller banks became a primary investor in the mezzanine tranches of bank TruPS CDOs, something that is also complicating regulators' resolutions of failed banks. To understand how this came about, the authors explore in detail the symbiotic relationship between dealers and rating agencies and how they modeled and sold TruPS CDOs. In their concluding comments, the authors provide several lessons learned for policymakers, regulators, and market participants.Asset-backed financing

The problems of assessing software reliability ...When you really need to depend on it

This paper looks at the ways in which the reliability of software can be assessed and predicted. It shows that the levels of reliability that can be claimed with scientific justification are relatively modest