A Modular Safety Assurance Method considering Multi-Aspect Contracts during Cyber Physical System Design

Designing safety-critical cyber physical systems (CPS) was and remains a challenging task. CPS engineers are supposed to design solutions that are easy to modify, reusable, satisfy certification authorities, meet safety goals, separate between concerns, etc. With these partly contradicting demands it sometimes is even impossible to find a viable CPS design. The idea using contract-based design methods has been around for over two decades and enables automating the (re-)validation of the specification of CPS against the surrounding system or operational environment. In this work we extend the notion of contracts by component and interface contracts and give ideas on how to integrate them in a modular safety assurance approach. The explicit separation between these two types of contracts also better reflects the separation of concerns and reduces the overall modeling effort. We evaluate our approach with an automotive E-Drive case study.