A Pattern-based Approach towards Modular Safety Analysis and Argumentation

abstract

Safety standards recommend (if not dictate) performing many analyses during the concept phase of development as well as the early adoption of multiple measures at the architectural design level. In practice, the reuse of architectural measures or safety mechanisms is widely-spread, especially in well-understood domains, as is reusing the corresponding safety-cases aiming to document and prove the fulfillment of the underlying safety goals. Safety-cases in the automotive domain are not well-integrated into architectural models and as such do not provide comprehensible and reproducible argumentation nor any evidence for argument correctness. The reuse is mostly ad-hoc, with loss of knowledge and traceability and lack of consistency or process maturity as well as being the most widely spread and cited drawbacks. Using a simplified description of software functions and their most common error management subtypes (avoidance, detection, handling, ..) we propose to define a pattern library covering known solution algorithms and architectural measures/constraints in a seamless holistic model-based approach with corresponding tool support. The pattern libraries would comprise the requirement the pattern covers and the architecture elements/ measures / constraints required and may include deployment or scheduling strategies as well as the supporting safety case template, which would then be integrated into existing development environments. This paper explores this approach using an illustrative example.