A Method to Support the Accountability of Safety Cases by Integrating Safety Analysis and Model-Based Design

In this paper, we describe a method of visualizing the behavior of systems’ failures in order to improve the explanatory ability of safety analysis artifacts. Increasingly complex in-vehicle systems are making traditional safety analysis artifacts more difficult for reviewers to understand. One of the requirements for improvement is to provide more understandable explanations of failure behaviors. The AIAG/VDA FMEA (Failure Mode and Effect Analysis) handbook, published in 2019, introduced the FMEA-MSR (Supplemental FMEA for Monitoring and System Response) to explicitly describe the behavior of failures called the Hybrid Failure Chain (e.g., chain of failure mode, failure cause, monitoring, system response, and failure effects). For more precise explanations of the safety analysis artifacts, we propose a method to integrate and visualize failure behaviors into architectural design diagrams using SysML. Based on FTA (Fault Tree Analysis) and FMEA results, along with SysML diagrams (e.g., internal block diagrams), the proposed method imports represent FMEA and FTA data graphically as Hybrid Failure Chains with a system model to improve information cohesion in the safety analysis artifact. We found that the proposed method facilitates the discovery or recognition of flaws and omissions in the fault model.