Development of an on board real time expert system for controlling engineering systems requires tradeoffs between AI and real time approaches. The article presents an alternative that lies between embedding AI in real time and embedding real time in AI. We used this framework to develop an expert system development environment for maintaining and updating information about an evolving system as its state changes because of abnormal events such as faults, or as a consequence of external actions taken upon the system. We've successfully applied it in several engineering domains such as process control, medical monitoring, and onboard diagnosis. The author explains how it was applied to a system that controls automobile manoeuvring.