Constructing Product-Line Safety Cases from Contract-Based Specifications

Safety cases are used to argue that safety-critical systems satisfy the requirements that are determined to mitigate the potential hazards in the systems operating environment. Although typically a manual task, safety cases have been successfully created for systems without many configuration options. However, in highly configurablesystems, typically developed as a Product Line (PL), arguing about each possible configuration, and ensuring the completeness of the safety case are still open research problems. This paper presentsa novel and general approach, based on Contract-Based Specification(CBS), for the construction of a safety case for an arbitrary PL. Starting from a general CBS framework, we present a PL extension that allows expressing configurable systems and preserves the properties of the original CBS framework. Then, we define the transformation from arbitrary PL models, created using extended CBS framework, to a safety case argumentation-structure, expressed using the Goal Structuring Notation. Finally, the approach is exemplified on a simplified, but real, and currently produced system by Scania CV AB.QC 20190521