SAFETY ASSESSMENT MODEL OF SOFTWARE FOR FAILURE DIAGNOSIS SYSTEMS

The software for a failure diagnosis system can be represented in terms of production rules; the condition part represents a system failure condition and the conclusion part corresponds to a cause of the system failure or an appropriate protective action to be taken. This paper proposes a safety assessment model of the software to evaluate its contribution to the risk caused by the entire failure diagnosis system. The proposed risk criterion considers not only the reliability of hardware components of the failure diagnosis system, but also the reliability characteristics of the system to be monitored. Conventional verification and validation methods of rule-based systems assume that the software reliability can be achieved by maintaining the consistent relation between condition parts and conclusion parts. However, the risk criterion derived in this paper shows that the software for a failure diagnosis system cannot be optimized without considering these environmental factors.