On The Relationship Between User Models And Discourse Models

The best way to summarize my view of the relationship between user models and discourse models is that they are separate, but related to each other. This paper will show why the two terms have completely distinct elements, and where the common ground between the two lies. It is also important to acknowledge at the outset that the two terms have not been well defined in the literature. For the discourse model, I am including everything that should be derived from an analysis of discourse, to present a representation for the structure of the discourse, useful in subsequent responses. In this sense, I focus on the interpretation of a discourse from the point of view of one of the conversants. I essentially include in the discourse all the components covered by the model of Grosz and Sidner (1986). For the definition of the user model, I also ground the discussion in the point of view of one conversant. The model is thus an analysis of the other conversant (subsequently referred to as the speaker). The term user model is especially obscure, because in the context of this journal it is confined to a derivation of background knowledge and goals of a user which influence the language used in the discourse. (One can use a similar term in the design of graphical interfaces, for instance). The discourse model must thus contain the following key elements: an indication of the structure of the discourse and an organization of the objects of the real world mentioned in the discourse (to help anaphora resolution, for example). As soon as this kind of history of objects is included (covered in the model of Grosz and Sidner (1986) by tracking attentional state and the objects currently in focus), there are elements that are not specifically attached to the user himself. The structure of the discourse is essentially provided in two different ways. Which of the actual utterances of the discourse group together into logical segments is covered by the "linguistic structure" of Grosz and Sidner (1986). Often clue words (such as "but anyway") will indicate how to segment the utterances into logical segments, without concern for how individual utterances within that segment relate. In addition, there is an indication of the intentional structure. Here, I would reinterpret slightly the term as used in Grosz and Sidner (1986) (see Cohen 1986). Intentional structure should indicate the intentional relations between, again, actual utterances. For instance, it is important to determine the cases where the goal underlying an utterance "contributes to the satisfaction of" the goal underlying another utterance--e.g., getting the hearer to believe some proposition p contributes to the satisfaction of getting the hearer to believe some proposition q (determined as dominance relations in Grosz and Sidner (1986). In this sense, my interpretation of the derivation of intentional structure agrees well with Wahlster's appeal for an incremental derivation of the discourse model). I believe that the intentional structure is related to, but not identical with, the plan of the speaker underlying discourse. For one, the plan of the speaker can be reconstructed at a different level of detail than what is actually uttered. For an example, see Appendix 1. This leads me to where I feel the discourse model and user model relate. The plan of the speaker underlying discourse is one part of the user model and is related to the intentional structure of the discourse. But there is more to the user model as well. There has been a good deal of work on co-operative responses (e.g., Joshi et al. (1984)). Van Beek (van Beek and Cohen 1986, van Beek 1986) shows that goals and systemwide preferences of a user can influence appropriate responses (e.g., preferring to take numerical analysis courses in a course advisor domain). It is thus important to include a model of the user's goals (beyond an understanding of the goal underlying each individual utterance, useful for the reconstruction of the intentional structure). This kind of