Planning For Intentions With Rhetorical Relations

A viable model of interactive discourse must explain how interlocutors share conversational control to construct the discourse, and recognize the contributions of others to it. The position that I take in this paper is from a narrower perspective, one in which there is a primary speaker who controls and directs the discourse, but that does so while trying to accommodate the informational needs of someone who primarily listens, and who believes what the speaker has to say. From this perspective, I will argue that speakers realize their intentions by conveying rhetorical relations. With the primary speaker's intent understood, I maintain that the primary listener's contribution prompts the speaker to express his intent with rhetorical relations that satisfy the listener's informational needs. Both the intentions of the primary speaker, and the primary listener's feedback are interpreted in the context of their shared beliefs about the domain, their shared beliefs about the discourse that has been constructed so far, and their common, language-based knowledge of possible extensions to it. Researchers have argued for several years that communicative intent not only exists, its recognition by a listener is essential in order for communication to occur [Aus62, Gri69, GS86]. More recently, Mann and Thompson have proposed that the juxtaposition of propositional content communicates one or more rhetorical relations [MT87]. Their theory, Rhetorical Structure Theory (RST), explains coherent text structure in terms of a set of rhetorical relations that exist between units of text. The model that I use for planning discourse about domain plans in interactive settings was developed under the assumption that intentions and rhetorical relations exist, and that the relations that a speaker chooses to express are appropriate to conveying her underlying intentions [Hal93]. These assumptions are consistent with views that have been expressed by others [Kib93, KK93, Lim93, Mai93, MP93, Tra93]. The following dialogue illustrates a relationship between intentions and rhetorical relations that my model captures: