Software fault-freeness and reliability predictions

Many software development practices aim at ensuring that software is correct, or fault-free. In safety critical applications, requirements are in terms of probabilities of certain behaviours, e.g. as associated to the Safety Integrity Levels of IEC 61508. The two forms of reasoning - about evidence of correctness and about probabilities of certain failures -are rarely brought together explicitly. The desirability of using claims of correctness has been argued by many authors, but not been taken up in practice. We address how to combine evidence concerning probability of failure together with evidence pertaining to likelihood of fault-freeness, in a Bayesian framework. We present novel results to make this approach practical, by guaranteeing reliability predictions that are conservative (err on the side of pessimism), despite the difficulty of stating prior probability distributions for reliability parameters. This approach seems suitable for practical application to assessment of certain classes of safety critical systems

Formal Methods For Life-Critical Software

The use of computer software in life-critical applications, such as for civil air transports, demands the use of rigorous formal mathematical verification procedures. This paper demonstrates how to apply formal methods to the development and verification of software by leading the reader step-by-step through requirements analysis, design, implementation, and verification of an electronic phone book application. The current maturity and limitations of formal methods tools and techniques are then discussed, and a number of examples of the successful use of formal methods by industry are cited

System survivability: a critical security problem

Purpose – This paper seeks to delve into the concept of determining the survivability of critical infrastructure in society, especially information‐based networks. Design/methodology/approach– Discusses the need for and the importance of an analysis language called EASEL, which aids in determining the survivability of critical systems through the use and creation of emergent simulations. Findings – Much of what has been presented here is still in its conceptual and research stage. There is still much to determine and define in this new research discipline of survivability. The survivability of critical systems can be determined by utilizing EASEL simulations to describe security situations. Originality/value – Armed with the knowledge gained in this paper, it is hoped that organizations can adopt strategies to protect their information systems and make them resilient and survivable