Combining disparate sources of information in the safety assessment of software-based systems

The main topic of the paper is a discussion on how to combine disparate sou rces of information in the safety assessment of software-based systems. Thi s is based on experience gained through the licensing process of a programm able system in the Swedish nuclear power plant Ringhals, where a guideline for reviewing software in safety-related systems was applied. One lesson le arned from this activity is that the approval of a programmable safety crit ical system, in particular one which is based on Commercial-Off-The-Shelf s oftware, is based on a combination of disparate sources of information. Thi s combination of information is made in a diagrammatic framework. An emergi ng methodology to combine information about disparate evidences in a system atic way is based on Bayesian Belief Networks. The objective is to show the link between basic information and the confidence one can have in a system . (C) 2000 Elsevier Science S.A. All rights reserved.