Elicitation and Specification of Safety Requirements

In this paper we demonstrate how to derive software requirements from system safety analysis in such a way that they could be easily captured in a software specification. We propose an integral approach for incorporating results of fault tree analysis (FTA) and failure mode and effect analysis (FMEA) into the requirements specification. In our approach statecharts facilitate construction of a control system and serve as a basis for structuring and integrating results of FTA and FMEA. The use of statecharts as a communication media between safety and software engineers assists the process of requirements discovery. The approach is illustrated by excerpts from the development of realistic industrial system - the liquid handling workstation Fillwelltrade.