Classification of Safety Requirements for Formal Verification of Software Models of Industrial Automation Systems

By use of formal methods the trust in the safe function of software can be increased. But the use of formal methods in practical software development is rare. One of the reasons is difficulties arising from formal specification of safety requirements. In this paper characteristics of safety requirements of software models of industrial automation systems are analysed by classifying these requirements. Thereby different criteria of classification are important, especially terminology in industrial automation technology, formulation in natural language of safety requirements and constructs of the used formal language. In this paper constructs of the Computation Tree Logic (CTL) are considered. On the basis of this classification approaches to handle difficulties in formal specification of safety requirements by software engineers are shown. Key-words: safety critical industrial automation systems, safety requirements, formal verification, model checking, formal specification, software specification, computation tree logic 1 This work was sponsored by the German Research Council (DFG) within the scope of the focus area program (1064) on the “Integration of Specification Techniques with Applications in Engineering” In Proceedings of 13 International Conference on Software and Systems Engineering and their Applications (ICSSEA) 2000, CNAM – Paris, France