Contract-based Safety: Specification and Application Guidelines

Markus Oertel and Ahmed Mahdi and Eckard Böde and Achim Rettberg
Proceedings of the 1st International Workshop on Emerging Ideas and Trends in Engineering of Cyber-Physical Systems (EITEC 2014)
Research related to qualification and certification of safety properties is mainly driven by two objectives, that are currently being addressed independently: the creation of reusable and modular safety cases as well as the direct integration of safety properties in the model based development artifacts abandoning separate analysis models. In this paper, we present a contract based specification approach allowing to reason about fault containment properties of components in a modular, reusable way. We link formalized safety requirements to typical development models like EAST-ADL, Simulink and AUTOSAR to state the needed properties and relations enabling analyzability of systems without any changes in industrial format, tool-chains and processes. The identification of the necessary safety artifacts to express safety concepts has been performed based on the ISO 26262, but can be applied also to other safety standards. Furthermore, we provide step-by-step application guidelines for the specification of safety concepts that can also be applied by engineers without a background in formal methods. The specification covers all typical areas of safety concepts like definitions of faults/failures, fault containment, expression of safety mechanisms or handling of degradation modes and safe states at multiple abstraction levels. Although the mainfocus is on the specification, we shortly introduce the possible analysis targets and clarify the interface between the safety view and the functional design. Finally, the approach is applied to a case study.
Combined Model-based Analysis and Testing of Embedded Systems