Hazard Relation Diagrams

Abstract

This talk is based on a paper published in the Requirements Engineering Journal in May 2017. During the development of safety-critical systems, the development process must ensure that requirements, which are defined to mitigate a hazard, are adequate. Adequacy of such hazard-mitigating requirements (HMRs) means that the requirements may not oppose the system’s operational purpose and must sufficiently avoid, reduce, or control, the occurrence of the conditions that trigger the hazard. However, information about the occurrence of the hazard’s trigger conditions are a work product of hazard analyses during early stages of safety assessment, while HMRs are a work product of requirements engineering. Dependencies between HMRs and hazard analysis results are implicit and tacit. In consequence, there’s a risk that during validation, inadequacy of HMRs regarding their ability to mitigate a hazard remains covert. The result may be that the system is assumed to be safe, but in fact may still cause injury or death. We introduced Hazard Relation Diagrams (HRDs) as a means to integrate and graphically visualize hazard analysis results with HMRs. Herein, we also provide insights into their empirical evaluation and show that HRDs increase objectivity in rationales containing adequacy judgments.