Safe Architectural Design Principles

This report discusses architectures for safety-critical systems. The report summarises the existing literature in the area as well as the guidance provided by existing safety-critical system development standards. We discuss the three constituent functions of fault tolerant architectures: error detection, damage assessment and confinement and error recovery. We also consider methods for fault prevention

Hazard Analysis of Interactive Systems

This report discusses approaches to analysis of safety-critical systems for operator error. The report summarises the existing literature in the area as well as the guidance provided by existing safety-critical system development standards

Derivation of Safety Requirements for Simple Computer-Based Control Systems

s and compressed postscript files are available via http://svrc.it.uq.edu.au. 1 Derivation of Safety Requirements for Simple Computer-Based Control Systems Brenton Atchison, Peter Lindsay Software Verification Research Centre School of Information Technology The University of Queensland Queensland 4072, Australia email: brenton, [email protected] Abstract Current best practice is that the acceptability of safety-critical software-based systems should be justified by a clear and defensible argument. This paper examines the structure that such an argument might take with regard to the allocation of system safety requirements to components, in particular software component requirements. A model solution is presented for a general class of control systems and application of the approach is illustrated with a case study. Keywords: safety-critical, process-control, software 1 Introduction Software-based systems are increasingly being used in safety critical applications wh..

A Case Study in Software Safety Assurance Using Formal Methods

s and compressed postscript files are available via http://svrc.it.uq.edu.au. 1 A Case Study in Software Safety Assurance Using Formal Methods Brenton Atchison, Peter Lindsay, David Tombs Software Verification Research Centre School of Information Technology The University of Queensland Queensland 4072, Australia email: {brenton,pal,tombs}@svrc.uq.edu.au Abstract This report describes a formal approach to verification and validation of safety requirements for embedded software, by application to a simple control-logic case study. The logic is formally specified in Z. System safety properties are formalised by defining an abstract model of the system's physical behaviour in Z, including its hazardous states and dominant sensor failures. The Possum specification-animation tool is then used to check that the logic meets its safety requirements. Finally, the logic is implemented in SPARK Ada and SPARK Examiner is used to formally verify the implementation meets its specification. Des..

Safety validation of embedded control software using Z animation

Describes a rigorous approach to safety validation of embedded control software by specification animation. The software control logic is specified in Z and systematically animated together with a model of the equipment under control. All reachable equipment states under software control are systematically identified and compared with known hazardous states in normal operation and under dominant failure conditions. The process is completely automated, removing the need for human intervention and associated errors, and can be applied much earlier than traditional test-based techniques. As a result, the validation method has the potential to provide cost-effective, high-integrity safety assurance for embedded software. The approach is illustrated with a hypothetical industrial press control syste