The use of Bayesian Belief Networks for combining disparate sources of information in the safety assessment of software based systems

This paper discusses some software safety standards, with respect to how they can be used tomeasure software safety. The possibility to transfer the requirements of a software safetystandard into Bayesian Belief Nets is also investigated. The aim is to utilise the BBNmethodology and associated tools, to transfer the software safety measurement into aprobabilistic quantity. In this way software can be included in probabilistic safety analysis ofthe total programmable system. A project was performed in which the method was appliedfor evaluation of a real, safety related programmable system that was developed according tothe avionic standard DO-178B. The test case, the standard, and the BBN methodology areshortly described, followed by a description of the construction of the BBN used in thisproject. Also a summary of some of the findings and experiences from the study is provided.