A Model-Oriented Approach to Safety Analysis Using Fault Trees and a Support System

Fault tree technique has been used in industry for safety analysis of safety critical systems for decades. They can be used for analysing the safety of both software and hardware. However, there are a lot of problems in ensuring the internal consistency and validity of fault trees constructed due to the absence of appropriate approach of using fault tree technique. This paper describes a model-oriented approach for safety analysis using fault trees. It advocates that a safety analysis of a system should start with a systematic study of the physical model of the system and, as a result, construct a system safety model based on the physical model. Then, further safety analysis of the system based on the system safety model by constructing fault trees is carried out. The internal consistency and consistency with the system safety model of these fault trees must be ensured. A prototype called FTSS (Fault Tree Support System) has been implemented by the ASAM (A Safety Argument Manager) project to support this approach, and its functionality is described.