Using Linguistic, World, And Contextual Knowledge In A Plan Recognition Model Of Dialogue

This paper presents a plan-based model of dialogue that combines world, linguistic, and contextual knowledge in order to recognize complex communicative actions such as expressing doubt. Linguistic knowledge suggests certain discourse acts, a speaker's beliefs, aud the strength of those beliefs; contextual knowledge suggests the most coherent continuation of the dialogue; and world knowledge provides evidence that the applicability conditions hold for those discourse acts that capture the relationship of the current utterance to the discourse as a whole. 1 Introduction Recognizing the roles that utterances play in a dialogue and how the utterances should be interpreted in the context of preceding dialogue is a crucial part of a robust model of understanding. In order to perform this recognition, our tripartite plan-based model of dialogue identifies not only domain and problem-solving actions but also discourse or communicative actions that determine how utterances relate to each other. For this communicative action recognition, we combine information gleaned from a variety of knowledge sources: contextual, linguistic, and world knowledge. The combination of these different knowledge sources enables the recognition of complex communicative actions such as expressing donbt. Although our tripar-tite model recognizes three different kinds of actions (domain, problem-solving, and discourse), the focus of this paper will be the recognition of discourse actions and how a combination of knowledge sonrces enables us to perform this recognition. A number of researchers have contended that a coherent discourse consists of segments that are related to one another through some type of structuring relation [Gri75, MT83] or have modeled discourse based on the semantic relationship of individual clauses [Pol86] or groups of clauses [Rei78]. But all of these fail to capture the goal-oriented natnre of discoursc. Grosz and Sidner [GS86] argue that recognizing the structural relationships among the intentions underlying a The ~overrlnlellt h&s cer-tMn rights in tiffs material. discourse is necessary to identify discourse structure; although they do not provide the details of a computational mechanism for recognizing these relationships, they do argue convincingly that it requires multiple knowledge sources. We have developed a plan-based model of dialogue and have incorporated into our model Grosz and Sidner's claim that linguistic, contextual, and world knowledge should be combined in recognizing the role of an utterance in a discourse.. We contend that at least three kinds of actions , domain, problem-solving, and discourse, should be captured by a model of task-oriented dialogue. have demonstrated that recognition of …