Arguing from Hazard Analysis in Safety Cases: A Modular Argument Pattern
This work addresses the need for more concrete and traceable safety arguments in safety-critical systems, though it appears incremental as it builds on existing hazard analysis methods.
The paper tackles the problem of safety arguments being too abstract, which reduces confidence, by proposing a modular argument pattern that integrates hazard analysis techniques (FTA, FMEA, STPA) with safety measures to improve argument construction.
We observed that safety arguments are prone to stay too abstract, e.g. solutions refer to large packages, argument strategies to complex reasoning steps, contexts and assumptions lack traceability. These issues can reduce the confidence we require of such arguments. In this paper, we investigate the construction of confident arguments from (i) hazard analysis (HA) results and (ii) the design of safety measures, i.e., both used for confidence evaluation. We present an argument pattern integrating three HA techniques, i.e., FTA, FMEA, and STPA, as well as the reactions on the results of these analyses, i.e., safety requirements and design increments. We provide an example of how our pattern can help in argument construction and discuss steps towards using our pattern in formal analysis and computer-assisted construction of safety cases.