Planning Text for Advisory Dialogues

PLANNING TEXT FOR ADVISORY DIALOGUES" Johanna D. Moore UCLA Department of Computer Science and USC/Information Sciences Institute 4676 Admiralty Way Marina del Key, CA 90292-6695, USA C~cile L. Paris USC/information Sciences Institute 4676 Admiralty Way Marina del Key, CA 90292-6695, USA ABSTRACT Explanation is an interactive process re- quiring a dialogue between advice-giver and advice-seeker. In this paper, we argue that in order to participate in a dialogue with its users, a generation system must be capable of reasoning about its own utterances and there- fore must maintain a rich representation of the responses it produces. We present a text planner that constructs a detailed text plan, containing the intentional, attentional, and .,,e~,~nc~ ~tructures of the text it generates. INTRODUCTION Providing explanations in an advisory situa- tion is a highly interactive process, requiring a dialogue between advice-giver and advice- seeker (Pollack eta/., 1982). Participating in a dialogue requires the ability to reason about previous responses, e.g., to interpret the user's follow-up questions in the context of the on- going conversation and to determine how to clarify a response when necessary. To pro- vide these capabilities, an explanation facility must understand what it was trying to convey and how that information was conveyed, i.e., the intentional structure behind the explana- tion, including thegoal of the explanation as a whole, the subgoal(s)of individual parts of the explanation, and the rhetorical means used to achieve them. Researchers in natural language under. standing have recognized the need for such information. In their work on discourse anal- ysis, Grosz and Sidner (1986) argue that it is necessary to represent the intentional struc- ture, the attentional structure (knowledge about which aspects of a dialogue are in focus at each point), and the linguistic structure of "The research described in this paper was sup- ported by the Defense Advanced Research Projects Agency (DARPA) under a NASA Ames cooperative agreement number NCC 2-520. The authors would like to thank William Swartout for comments on ear- lier versions of this paper. 203 the discourse. In contrast, most text gener- ation systems (with the notable exception of KAMP (Appelt, 1985)) have used only rhetor- ical and attentional information to produce coherent text (McKeown, 1985, McCoy, 1985, Paris, 1988b), omitting intentional informa- tion, or conflating intentional and rhetorical information (Hovy, 1988b). No text gener- ation system records or reasons about the rhetorical, the attentional, as well as the in- tentional structures of the texts it produces. In this paper, we argue that to success- fully participate in an explanation dialogue, a generation system must maintain the kinds of information outlined by Grosz and Sidner as well as an explicit representation of the rhetorical structure of the texts it generates. We present a text planner that builds a de- tailed text plan, containing the intentional, attentional, and rhetorical structures of the responses it produces. The main focus of this paper is the plan language and the plan structure built by our system. Examples of how this structure is used in answering follow- …

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