Session 5: Discourse

The fundamental problem in discourse is "What structure is there in discourse above the level of the sentence?" This question can be asked in terms of text versus dialogue. Is there a kind of structure that is exhibited in text but not in dialogue, or in dialogue but not in text? What are the appropriate structural descriptions of text and of dialogue? The question can also be asked from the perspective of recognition and from the perspective of generation. There is the structure that the speaker puts there and the structure the hearer discovers there. Are these the same? Does one have primacy over the other? For example , does the speaker impose the structure so that it is the job of the hearer to discover it, no matter what it is, or is it necessary for the speaker to design his discourse in a way that makes it as easy as possible for the hearer to interpret? The four papers in this session discuss various aspects of this family of questions. The first paper, by Liddy and her colleagues at Syra-cuse University, is concerned with text rather than dialogue , and recognition rather than generation. Structure in text can be studied from a general point of view or from a genre-specific point of view. This paper examines the structure specific to the genre of newspaper articles. The structure found can be in the form of a hierarchy, a tree-like structure, much like the syntactic structure of sentences, or it can consist of a division of the text into segments of various kinds, performing various functions, such as the Lead, the Main Body, and so on. Liddy and her colleagues argue that the latter kind of structure is more appropriate for newspaper articles. Among the questions addressed in this paper are • What are the structural elements or possibilities? • How can they be recognized, computationally? • Once recognized, how can they be used? The remaining papers are concerned with dialogue. The key idea in investigations of discourse from an artificial intelligence perspective is that the structure of a dialogue is, or is at least derived from, the structure of the par-ticipants' plans. "Plan" here is meant in the AI sense of a hierarchical structure of causal relations, decomposing goals into subgoals, and these subgoals into further sub-goals, and so on. An utterance in a dialogue is an action in …