Assessment of programmable systems using Bayesian belief nets

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