A Strategy for the Development of Safety Critical Software

Abstract

The effective protection of nuclear reactors involves microprocessors running software which needs to be of very high integrity. This paper describes work performed with the aim of defining a development strategy for such software. The Vienna Development Method (VDM) was used to specify formally a system for which an informal specification already existed. SPADE-Pascal was identified as a suitable implementation language with the benefit of tools to support the verification process. The VDM specification was translated into Pascal in order to provide an animation which proved valuable in revealing errors. A more efficient implementation of part of the system was developed and shown to be correct. As a result of this work the authors propose a strategy in which VDM, Pascal and the SPADE tools are brought together to form a coherent and effective approach to the development of safety critical software.