An event-chain risk assessment model based on definition evolution in safety criterions

Risk assessment is the core work in system safety. However, when system safety originated, there remains controversial in conception of hazard, risk, and mishap. This could be well reflected in criterions. As we know, in system safety field, a series of MIL-STD-882 versions are the most widely used criterions. And the standards of ANSI/GEIA-STD-0010 series have been paid more attention recent years. Definitions of core concepts in system safety have been changing and evolving in different versions of MIL-STD-882(X) and ANSI/GEIA-STD-0010. This controversy is the nature problem of risk analysis. And the core of this controversy, especially in dynamic operational process assessment, is fixing the range of risk definition and formalizing the risk modeling language. Therefore, a fixed range and unified modeling language is required in system safety, which makes it possible to help safety engineers predominate the risk level and provide risk control measures. This paper purposes to tap the characters of concepts and category of risk assessment, then to provide a formal model of risk assessment containing both the static condition: hazard and the mishap dynamic process based on event-chain.