A Software Safety Requirements Elicitation Approach Based on Hazardous Control Action Tree Modelling

Software safety requirements are crucial for safety assurance of safety-critical software systems. A novel accident causality model, Systems-theoretic accident modeling and processes (STAMP), has been proposed to overcome the limitations of traditional safety techniques in software safety requirements elicitation. However, the STAMP-based method is ad-hoc with no rigorous procedure to elicit software safety requirements effectively. Furthermore, the time-related safety requirements, which are important to software safety, have been paid little attention in STAMP-based method. With the purpose of overcoming these limitations, this paper strives to find a systematic approach to elicit software safety requirements with STAMP, especially the time-related safety requirements. Firstly, a new process model of STAMP is proposed to model all the system varilables and the ralationship of them in control processes. Then based on the process model, an approach HCAT-SSRA is proposed to elicit the software safety requirements by building Hazardous control action tree (HCAT) for each control action in system control processes. Additionally, several rules are proposed to guide time-related software safety requirements analysis. Finally, a case study is given to illustrate the availability and feasibility of the proposed method.