Two components of an action language

Abstract

Some of the recent work on representing action makes use of highdlevel action languages. In this paper we show that an action language can be represented as the sum of two distinct parts: an “action description language” and an “action query language.” A set of propositions in an action description language describes the effects of actions on states. Mathematically, it defines a transition system of the kind familiar from the theory of finite automata. An action query language serves for expressing properties of paths in a given transition system. We define the general concepts of a transition system, of an action description language and of an action query language, give a series of examples of languages of both kinds, and show how to combine a description language and a query language into one. This construction makes it possible to design the two components of an action language independently, which leads to the simplification and clarification of the theory of actions.