Subgoal Semantics in Agent Programming

This paper investigates the notion of subgoals as used in plans in cognitive agent programming languages. These subgoals form an abstract representation of more concrete courses of action or plans. Subgoals can have a procedural interpretation (directly linked to a concrete plan) or a declarative one (the state to be reached as represented by the subgoal is taken into account). We propose a formal semantics for subgoals that interprets these declaratively, and study the relation between this semantics and the procedural subgoal semantics of the cognitive agent programming language 3APL. We prove that subgoals of 3APL can be programmed to behave declaratively, although the semantics is defined procedurally.