PEX: a reactive procedure based decision maker [Satellite control application]

Presents a system called PEX (Procedure Expert), relying on M. Georgeff´s ideas (1985). The authors introduce the concept of `integrity context´ as a procedure relevance criterion to increase reactivity. The authors envisage a procedure-based process control system. The purpose of the procedural decision maker (PDM) is to make the physical system reach a given objective. It exploits a procedural model which maps objectives and behavioral information (procedures) for deciding in real time what commands should be emitted and when. The authors consider reactivity as first (R1) the aptitude to dynamically choose the appropriate procedures according to the actual system´s state, and second (R2) the aptitude to monitor the relevance of the procedure being executed with respect to the current system´s behavior. The authors show how to confer on the PDM the potential to be reactive by allowing an appropriate knowledge representation, and suggest a clean mechanism to take advantage of it. The analysis consists in enriching the Knowledge Areas (KA) representation language and designing a smart KA interpreter specialized in particular on reactivity of the R2 type