A method to generate reusable safety case argument-fragments from compositional safety analysis

Safety-critical systems usually need to be accompanied by an explained and well-founded body of evidence to show that the system is acceptably safe. While reuse within such systems covers mainly code, reusing accompanying safety artefacts is limited due to a wide range of context dependencies that need to be satisfied for safety evidence to be valid in a different context. Currently, the most commonly used approaches that facilitate reuse lack support for systematic reuse of safety artefacts. To facilitate systematic reuse of safety artefacts we provide a method to generate reusable safety case argument-fragments that include supporting evidence related to compositional safety analysis. The generation is performed from safety contracts that capture safety-relevant behaviour of components in assumption/guarantee pairs backed up by the supporting evidence. We evaluate the feasibility of our approach in a real-world case study where a safety related component developed in isolation is reused within a wheel-loader.