Intention Is Commitment with Expectation

Modal logics with possible worlds semantics provide a means to describe the rational behavior of agents in terms of mental states, such as beliefs, goals, and intentions. Agent’s beliefs and goals are typically represented in these logics by primitive modal operators. However, the representation of agent’s intentions varies greatly between theories. Some logics characterize intention as a primitive operator, while others define intention in terms of more primitive constructs. Taking the latter approach is a theory due to Cohen and Levesque (Cohen & Levesque 1990), under which intentions are a special form of commitment or persistent goal. The theory has motivated theories of speech acts and joint intention and innovative applications in multiagent systems and industrial robotics. However, Singh (Singh 1992) shows the theory to have certain logical inconsistencies and permit certain absurd scenarios. We present a modification of the theory that preserves the desirable aspects of the original while addressing the criticism of Singh. This is achieved by the introduction of an additional operator describing the achievement of expectations, refined assumptions, and new definitions of intention. The modified theory gives a cogent account of the rational balance between agents ’ action and deliberation, and suggests the use of means-ends reasoning in agent implementations