A Collaborative Planning Approach to Discourse Understanding

Abstract

Approaches to discourse understanding fall roughly into two categories: those that treat mental states as elemental and thus reason directly about them, and those that do not reason about the beliefs and intentions of agents themselves, but about the propositions and actions that might be considered objects of those beliefs and intentions. The first type of approach is a mental phenomenon approach, the second a data-structure approach (Pollack, 1986b). In this paper, we present a mental phenomenon approach to discourse understanding and demonstrate its advantages over the data-structure approaches used by other researchers. The model we present is based on the collaborative planning framework of SharedPlans (Grosz and Sidner, 1990; Lochbaum, Grosz, and Sidner, 1990; Grosz and Kraus, 1993). SharedPlans are shown to provide a computationally realizable model of the intentional component of Grosz and Sidner's theory of discourse structure (Grosz and Sidner, 1986). Additionally, this model is shown to simplify and extend approaches to discourse understanding that introduce multiple types of plans to model an agent's motivations for producing an utterance (Litman, 1985; Litman and Allen, 1987; Lambert and Carberry, 1991; Ramshaw, 1991).