TREE-EXPERT: a tree-based expert system for fault tree construction

This paper addresses the topic of automatic fault tree construction, utilizing an expert system with Artificial Intelligence (AI) techniques and presents the related software tool, TREE-EXPERT—an expert system for automatic fault tree construction. In the light of the features involved in developing a fault tree, a new and more reasonable structure of knowledge representation, which is knowledge tree based, has been established. The knowledge tree provides the means by which component failure behaviors can be described by a group of particular fault tree modules instead of production rules. By introducing the conditional branch function, the new design of the knowledge base incorporates many good features such as strong expressivity, flexibility and ease of extension and it takes advantage of the user's familiarity with the field of fault tree analysis. Additionally, the design of the inference engine is original in that it deals with nodes, which it treats, as special components, so that many complicated engineering cases, such as the application of success criteria, and the problems of flow diversions and flow reversals in a process system, can be well managed and the function of the expert system is improved as a whole. TREE-EXPERT can be used to deal with large-scale and complicated engineering systems, and many engineering factors can be considered, e.g. more than one system parameter and the effect on them switching of the system operating states, bi-directional inference, human error failure, common-cause failure, maintenance and test, etc. On the other hand, the software uses P & ID (Pipe & Instrument Diagram) type interface to describe the system topology, which provides an easier man-machine interface with powerful graphics functions. This software can handle not only ‘process’ systems but also, with appropriate additions to the generic knowledge base, electrical systems and other similar systems.