Generating Safety Verification Conditions Through Fault Tree Analysis and Rigorous Reasoning

An approach based on informal, rigorous reasoning is described as a means of discovering “safety verification conditions” (SVCs). The approach can be carried out at various levels of detail. When the approach is carried out at the level of a “black box” view of the system, the result is a set of system safety requirements. The approach has similarities with Fault Tree Analysis (FTA) and Software Fault Tree Analysis (SFTA). Like FTA, a given hazard is traced backwards through the system to cover all the ways in which a hazardous condition can occur. Like SFTA, a “proof-by-contradiction” style reasoning is employed. The approach is illustrated by a detailed (hypothetical) chemical factory information system which is similar to other safety-related real-time information systems.