The Semantics of Intention Maintenance for Rational Agents

The specification, design, and verification of agent-oriented systems depends upon having clear, intuitive formalisms for reasoning about the properties of such systems. In this paper, we consider agents whose state comprises the three mental attitudes of belief, desire, and intention. While the static relationships among these entities has had considerable attention, the manner in which these entities change over time has not been formalized rigourously. By considering some simple examples, we show that the formalization of some of these intuitions is problematic. We then examine these intuitions from a possible-worlds perspective and formally describe the dynamics of intention maintenance in the context of changing beliefs and desires. To solve the problems identified in the examples, and to properly capture our semantic intuitions about intention maintenance, we extend the standard logics by introducing forms for only modalities of belief, desire, and intention, along the lines of Levesque's only believe operator. This allows us to formalize the process of intention maintenance. We conclude by comparing our work with other related work.