Representing Actions in Logic Programs and Default Theories: A Situation Calculus Approach

We address the problem of representing commonsense knowledge about action domains in the formalisms of logic programming and default logic. We employ a methodology proposed by Gelfond and Lifschitz which involves rst deening a high-level language for representing knowledge about actions , and then specifying a translation from the high-level action language into a general-purpose formalism, such as logic programming. Accordingly, we deene a high-level action language AC, and specify sound and complete translations of portions of AC into logic programming and default logic. The language AC includes propositions that represent \static causal laws" of the following kind: a uent formula can be made true by making a u-ent formula true (or, more precisely, is a caused whenever is). Such propositions are more expressive than the state constraints traditionally used to represent background knowledge. Our translations of AC domain descriptions into logic programming and default logic are simple, in part because the noncontrapositive nature of causal laws is easily reeected in such rule-based formalisms.