Representing Actions: Laws, Observations and Hypotheses

> We propose a modiication L 1 of the action description language A. The language L 1 allows representation of hypothetical situations and hypothetical occurrence of actions (as in A) as well as representation of actual occurrences of actions and observations of the truth values of uents in actual situations. The corresponding entailment relation formalizes various types of common-sense reasoning about actions and their eeects not modeled by previous approaches. As an application of L 1 we also present an architecture for intelligent agents capable of observing, planning and acting in a changing environment based on the entailment relation of L 1 and use logic programming approximation of this entailment to implement a planning module for this architecture. We prove the soundness of our implementation and give a suucient condition for its completeness. <