Hazard and operability study as an approach to software safety assessment

Hazard and operability study (HAZOP) is an analytical technique that uses the imagination and experience of experts to identify potential accidents. Lloyd´s Register has used HAZOP techniques for many years and is now focusing its attention on the application of this method to computer systems. This paper is a review of the HAZOP method and specific experience related to software assessment. The selection of representations in the generation of models for particular systems containing software is illustrated using examples from Lloyd´s Register´s current public domain research and development programme. HAZOP brings the experience of a team to bear on all aspects of a system´s design. It offers a well developed process for testing a system´s design against a standard of safe operation. As well as specifying the cause and location of faults, HAZOP usually provides a rich enough hazard description to act as a specification for redesign, The special benefit of HAZOP for software analysis is in identifying the interaction effects between the software, its computer environment and the real world in which it is used