System safety model and simulation based on entity-oriented event sequence diagram

An accident is regarded as an emergent phenomenon in the complex socio-technical systems, so the systemic accident models should be created to adapt the complex characteristics. Event Sequence Diagram (ESD) has been used for PRA in many industries, which can present an accident scenario visually by describing the sequence of events ordered in time. But the ESD belongs to semi-dynamic because it represents system dynamics in a coarse partitioning of state space, and seldom analyzes the components relationships which are the important cause for emergent phenomenon. An event means the system states transformation which is caused by the behaviors of system components (entities) including technical, human and environments. So using entity and its behaviors, the accident events can be represented in more detail. Analyzing and abstracting the entities in the socio-technical system and their behaviors in the accident scenario, this paper tries to add new entity elements into the model to create Entity-Oriented ESD (EOESD). By the new elements, not only the event sequences but also the dynamic relations between system components in an accident can be included in the EOESD. A case study in the maritime industry is presented including the analysis conclusion to verify the feasibility of EOESD.