EXPLICIT AND IMPLICIT INDETERMINISM - REASONING ABOUT UNCERTAIN AND CONTRADICTORY SPECIFICATIONS OF DYNAMIC-SYSTEMS

A high-level action semantics for specifying and reasoning about dynam ic systems is presented which supports both uncertain knowledge (taken as explicit indeterminism) and contradictory information (taken as im plicit indeterminism). We start by developing an action description la nguage for intentionally representing nondeterministic actions in dyna mic systems. We then study the different possibilities of interpreting contradictory specifications of concurrent actions. We argue that the most reasonable interpretation which allows for exploiting as much in formation as possible, is to take such conflicts as implicit indetermi nism. As the second major contribution, we present a calculus for our resulting action semantics based on the logic programming paradigm inc luding negation-as-failure and equational theories. Soundness and comp leteness of this encoding wrt. the notion of entailment in our action language is proved by taking the completion semantics for equational l ogic programs with negation. (C) Elsevier Science Inc., 1997.