A. Saeed
R. de Lemos
T. Anderson
University of Newcastle upon Tyne. 1993
Requirements analysis plays a vital role in the development of safety-critical systems since any errors in the requirements specification will corrupt the subsequent stages of system development. Experience in safety-critical systems has shown that requirements specification errors can and do cause accidents. This paper presents a general framework for the formal specification and verification of the critical requirements in the development of safety-critical systems. The framework is based on a clear separation of the mission and critical issues during requirements analysis. Analysis of the critical issues is performed in two phases. The first phase identifies those "real world" properties relevant to the critical requirements: the physical laws or rules of operation, and the system hazards. In the second phase, the interface between the system and its environment is identified, and the behaviour required at this interface is specified. For each phase, due to its own characteristics, we propose the utilization of different formal models, respectively, a logical formalism (timed history logic) and a net formalism (predicate-transition nets). To illustrate the proposed framework an example based on a train set crossing is presented.