Attention, Intentions, And The Structure Of Discourse

In this paper we explore a new theory of discourse structure that stresses the role of purpose and processing in discourse. In this theory, discourse structure is composed of three separate but interre- lated components: the structure of the sequence of utterances (called the linguistic structure), a struc- ture of purposes (called the intentional structure), and the state of focus of attention (called the attentional state). The linguistic structure consists of segments of the discourse into which the utter- ances naturally aggregate. The intentional structure captures the discourse-relevant purposes, expressed in each of the linguistic segments as well as relationships among them. The attentional state is an abstraction of the focus of attention of the participants as the discourse unfolds. The attentional state, being dynamic, records the objects, properties, and relations that are salient at each point of the discourse. The distinction among these components is essential to provide an adequate explanation of such discourse phenomena as cue phrases, referring expressions, and interruptions. The theory of attention, intention, and aggregation of utterances is illustrated in the paper with a number of example discourses.

Introduction. An account of discourse structure is closely related to two questions: What individuates a discourse? What makes it coherent? That is, faced with a sequence of utterances, how does one know whether they constitute a single discourse, several (perhaps interleaved) discourses, or none? As we develop it, the theory of discourse struc- ture will be seen to be intimately connected with two nonlinguistic notions: intention and attention. Attention is an essential factor in explicating the processing of utterances in discourse. Intentions play a primary role in explaining discourse structure, defining discourse coher- ence, and providing a coherent conceptualization of the term "discourse" itself. 1981; Sidner 1983; 1985; Allen 1983, Litman 1985; Pollack 1986). Our goal has been to generalize these constructs properly to a wide range of discourse types. Grosz (1978a) demonstrated that the notions of focusing and task structure are necessary for understanding and producing task-oriented dialogue.

Discussion / Conclusion. The theory of discourse structure presented in this paper is a generalization of theories of task-oriented dialogues. It differs from previous generalizations in that it carefully distinguishes three components of discourse structure: one linguistic, one intentional, and one attentional. This distinction provides an essential basis for explaining interruptions, cue phrases, and referring expressions. The particular intentional structure used also differs from the analogous aspect of previous generalizations. Although, like those generalizations, it supplies the prin- cipal framework for discourse segmentation and deter- mines structural relationships for the focusing structure Although admittedly still incomplete, the theory does provide a solid basis for investigating both the structure and meaning of discourse, as well as for constructing discourse-processing systems. Several difficult research problems remain to be explored.