Dependable risk analysis for systems with E/E/PE components: Two case studies

Abstract

Accurate risk assessment of safety-related systems involving software is a hard engineering problem for well-known reasons. We present two case studies in the use of Ontological Hazard Analysis (OHA), a semi-formal method for hazard identification and analysis aiding Correct-by-Construction (CbC) approaches to developing such systems. OHA controls very carefully the means of expression of safety requirements, starting with a simple semi-formal language and proceeding to more expressive requirements through formal refinement, a decades-old technique for CbC program development developed in the computer-science theory community. In the case studies, the use of OHA allows the risk assessment of the systems through known techniques, avoiding the general problems posed by non-continuity which are inherent in attempting to assess the risk of systems based on software. © Springer-Verlag London Limited 2009.