Provably Correct Safety Critical Software

Abstract

We present the approach to development of provablycorrect safety critical software emerging through the case studies activity of the ProCoS project. We envisage the development of a safety critical system through six major stages; Control objectives and safety criteria will be be captured in requirements capture languages (RLs) (formal mathematical models of the problem domain) supporting the notions of durations, events and states. A specification expressed in a specification language(SL) satisfying the requirements is derived via requirements transformations.The specification is refined and finally transformed into a programming language (PL) program which is refined and mapped by a verified PL compiler onto the instruction set of an abstract hardware machine (AHM) and is executed via an ABM computer supported by a trusted kernel operating system. The aim of this paper is to show how the coordinated development activities fit together once an informal specification of the desired system behaviour has been delivered.