The Need For Intentionally-Based Approaches To Language

Evidence for the above claim comes from my recent work on understanding subdialogues in conversation [Loc93]. Following the work of Grosz and Sidner [GSg0], I view discourse behavior as an instance of the more general phenomenon of collaboration. For agents to successfully collaborate on a task, they must hold certain beliefs and intentions regarding the acts they will perform to accomplish that task. The definitions of the SharedPlan model of collaborative activity [GS90, LGS90, GK93] specify the requisite components of the mental states of collaborating agents and consequently provide an important context for interpreting their utterances. In particular, because agents are aware of the beliefs and intentions they must hold to have a SharedPlan, their utterances can be understood as contributing information towards the establishment of the appropriate mental states, and thus the building of such a plan. The process by which utterances are understood has been formalized in algorithms for augmenting the beliefs and intentions of an evolving SharedPlan, and used to explain utterances concerning the performance of actions [LGSg0, Locgl]. My current work [Loc93], based on Grosz and Sidner's theory of discourse structure [GS86], provides a new approach to the problem of understanding subdialogues and their relationship to the discourse in which they are embedded. The basic approach entails treating each subdialogue or discourse segment as a separate collaboration between the conversational participants; each utterance of a subdialogue is understood as contributing some information towards the completion of a SharedPlan. Because subdialogues do not occur in isolation, each subdialogue itself is understood in terms of the role its corresponding SharedPlan plays in satisfying the other SharedPlans underlying the dialogue. In particular, if the completion of the new SharedPlan contributes to the establishment of one of the beliefs or intentions necessary for the completion of another, then the first SharedPlan is said to be subsidiary to the second. A subsidiary relationship between SharedPlans corresponds to a dominance relationship [GS86] between discourse segment purposes; it provides an explanation [SI81] for why the dominated segment was initiated by a conversational participant I .