From Fault Tree Analysis to Runtime Model-Based Assurance Cases

Cyber-physical systems (CPSs) demand the justification of system safety and component reliability. Assurance cases provide an explicit means for justifying/assessing confidence in system dependability with explicit and implicit references to design, safety, and reliability artifacts. Fault Tree Analysis (FTA) is one of the most popular safety analysis techniques, which is an integral part of Model-Based Safety Analysis. Conversely, the open and adaptive nature of CPSs, demands a paradigm shift from design-time to runtime system assurance. Although the Structured Assurance Case Metamodel (SACM) provides the foundations for runtime system assurance, enabling the traceability between assurance cases and FTA results, which is part of Executable Digital Dependability Identities (EDDIs) of CPS components, it is still a barrier. In this paper, we introduce a model-driven methodology to support the synthesis of assurance cases from FTA as another step towards demonstration of CPS safety and component reliability at runtime.