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.

In this paper, we formally define Test Case Sequence Diagrams (TCSD) as an easy-to-use means to specify test cases for components including timing constraints. These test cases are modeled using the UML2 syntax and can be specified by standard UML-modeling-tools. In a component-based design an early identification of errors can be achieved by a virtual integration of components before the actual system is build. We define such a procedure which integrates the individual test cases of the components according to the interconnections of a given architecture and checks if all specified communication sequences are consistent. Therefore, we formally define the transformation of TCSD into timed-arc Petri nets and a process for the combination of these nets. The applicability of our approach is demonstrated on an avionic use case from the ARP4761 standard.