Knowledge-Based Support for Event Tree Construction

Abstract A prototype system called EventMAP has been developed to provide knowledge-based support for event tree construction. It comprehends an event tree model of a physical system, which represents the possible event sequences following an initial incident. This model can be used to identify potentially hazardous accident or failure scenarios, to help in assessing the possible outcomes of an observed incident, and to support decisions about appropriate actions. It can also be used during modification to provide insights into the needs for specific safety features. EventMAP incorporates explicit knowledge about safety engineering and good event tree construction practice. This assures that model building will be more systematic, and will produce more complete and correct event trees. Assumptions underlying the model are tracked explicitly, allowing ‘what-if’ exploration. Moreover, the safety-related design rationale will be preserved despite personnel changes over time. EventMAP incorporates knowledge about: plant structure in terms of subsystems, components, and interconnections; cause/effect relationships and other interactions among subsystems; and failure modes, including human errors. The role of EventMAP is to act as an ‘intelligent assistant’ for the event tree developer; it monitors the evolving model and issues suggestions and warnings to the user as appropriate.