Communication in safety cases-a semantic approach

In safety critical domains, meta-level requirements such as guidelines and regulations influence design. As well as stating properties which must hold of the final system, they shape the process of design from its inception through to its specification and implementation. By formalising these meta-level requirements, they can be made available for guiding and constraining the development of a design. In this way, building a safety case demonstrating that the derived specification satisfies the regulations can become an integral part of design. Subsequent design revisions are constrained to the framework of regulation. Similarly, the implications of revisions to meta-level requirements become assessable. We are formalising a range of documents relating to Shell Expro´s emergency shutdown systems. They include both meta-level requirements, in the form of a code of practice, and design documents ranging from high level outline to low level functionality. By representing each level of information, and making its semantics explicit, it becomes possible to generate significant sections of the lower levels, using control from meta-level requirements