Functional safety based on a system reference model

• Authors: Manfred Broy
• Venue: ASSC '12 Proceedings of the Australian System Safety Conference - Volume 145
• Year: 2012

Ensuring functional system safety comprises four major tasks. First, all possible hazards and risks of incidents with respect to functional safety have to be identified. Second, the system requirements specification must be shown to be valid in the sense that it excludes all the hazards with sufficiently high probability. Third, it has to be shown that the requirements are implemented correctly. Fourth, it must be demonstrated that for the implementation all possible failures of subsystems that could lead to violations of the functional safety requirements systems are excluded with a sufficiently high probability. This way it has to be shown that the specification and its implementation lead to an acceptable risk in terms of probabilities of violations of safety requirements. For a proper engineering of functional safety we suggest the use of a rigorous modelling framework. It consists of: a system modelling theory that provides a number of modelling concepts that are carefully related and integrated; a system reference model; and a reference architecture structuring systems into three levels of abstractions represented by views, including a functional view, a logical subsystem view and a technical view. It is demonstrated how, in this framework, all kinds of safety issues are expressed, analysed and traced; and how, due to the formalization of the framework, safety problems are formally analysed, specified and verified.