Justifying reliability claims for a fault-detecting parallel architecture

This paper describes ‘Goal Structuring Notation’ (GSN), a graphical notation that can be used to structure and present an argument justifying some aspect of system performance. The design of a fault-detecting processor pair is examined to determine the extent to which it is indeed ‘fault-detecting’. It is argued that for complex systems, difficulties with assessment arise not so much from a lack of analysis techniques, but from the need to integrate the results from many diverse analyses into a coherent and compelling argument. It is suggested that GSN provides a framework in which such an argument can be made.