Explicit and implicit indeterminism - Reasoning about uncertain and contradictory specifications of dynamic systems

A high-level action semantics for specifying and reasoning about dynamic systems is presented which supports both uncertain knowledge (taken as explicit indeterminism) and contradictory information (taken as implicit indeterminism). We start by developing an action description language for intentionally representing nondeterministic actions in dynamic 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 information as possible, is to take such conflicts as implicit indeterminism. As the second major contribution, we present a calculus for our resulting action semantics based on the logic programming paradigm including negation-as-failure and equational theories. Soundness and completeness of this encoding wrt. the notion of entailment in our action language is proved by taking the completion semantics for equational logic programs with negation. (C) Elsevier Science Inc., 1997.