A train set as a case study for the requirements analysis of safety-critical systems

Abstract

Requirements analysis plays a vital role in the development of safety-critical systems since any faults in the requirements specification will corrupt the subsequent stages of system development. Experience in safety-critical systems has shown that faults in the requirements can and do cause disasters. The analysis of the safety requirements of a train set system is discussed in terms of a general framework for the requirements analysis of safety-critical systems. This framework is based on the clear separation of the mission and safety issues, and also on the separation of the analysis, into two phases, to be performed in terms of the properties of the real world, I.e. physical laws and rules of operation, and the properties of the system, I.e. the mapping of the real world properties in terms of the system sensors and actuators. Due to the different expressive needs of the two phases we propose the utilisation of different formal models, respectively, a logical formalism (Timed History Logic) and a net formalism (Predicate-Transition nets). © 1992 The British Computer Society.