SIL4 process improvement with POSE and Alloy

Safety Standards demand that industrial applications demonstrate they have the required safety integrity and this starts with the initial requirements phase. This paper shows how the Problem Oriented Software Engineering (POSE) framework, in conjunction with the Alloy formal method, supports this task through its ability to elaborate, transform and analyse the project requirements and thus develop a solution for an avionics case study. In particular, this work reports on how the POSE/Alloy combination was used in conjunction with the POSE safety pattern to improve the requirements analysis capabilities of an existing, successful safety critical development process. The results of applying this combination to an existing design showed that it could detect anomalies early in the life cycle that had previously been detected by much later (and more costly) validation work.