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<Paper uid="J88-3011">
  <Title>USER MODELS AND DISCOURSE MODELS: UNITED THEY STAND . . .</Title>
  <Section position="4" start_page="0" end_page="0" type="concl">
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SUMMARY
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    <Paragraph position="0"> The above discussion demonstrates that the function of a UM and of all mentioned DM components can be completely fulfilled by the outlined belief~ goal, and plan maintenance system. I cannot deal here in detail with the question of whether this is also the case for other components that have been proposed for a DM, for example, the structuring of the dialog into dialog segments (Grosz Sidner 1986), a context space grammar (Reichman 1981), or rhetorical predicates (schemata; McKeown 1982). With respect to the analyzed components, we have seen that the discourse model almost completely overlaps with the user model at the level of content. Only if the user does not fully catch the system's dialog contributions are entries in the DM created which do not form part of the UM (see, for instance, Wahlster's example, this issue). But at a procedural level as well, only a few processes can be found which operate exclusively on that part of the user model that is identical with the discourse model, or upon the remaining parts of the user model.</Paragraph>
    <Paragraph position="1"> This large degree to which the DM is included in the UM, however, is not surprising: Discourse models are ultimately based on linguistic conventions. In order for the linguistic, intentional, attentional, etc., structure of the previous discourse to be exploited for future dialog contributions, conventions about what the structure of a particular ongoing dialog actually is must exist. Knowledge about convention is mutual knowledge, however, (Lewis 1969, Schiffer 1972), and thus part of MB. The same holds true for the above-mentioned additional components of the DM that could not be dealt with in this paper. And, by the way, it also holds true for the grammar the system employs (but see the opposing views of Morik and Wahlster, this issue). If the system did not assume that its assumptions about the syntactic structure of language (as expressed in its grammar) be Computational Linguistics, Volume 14, Number 3, September 1988 93 Alfred Kobsa &amp;quot;Jser Models and Discourse Models: United they stand... shared by the user, it could not justifiably use it in the analysis and generation of dialog contributions without risking miscommunication. And there definitely exists work in user modeling (e.g., Schuster I985, Kilbury 1986, Lehman CarboneU 1988), which is concerned with the recognition of those parts of a user's idiosyncratic grammar that deviate from the mutually shared kernel grammar. Of course, an entry in MB never means that the system assumes that the user &amp;quot;has the same structure in his/her mind&amp;quot; (e.g., ATNs, KL-ONE, or LISP), but only that these structures are functionally equivalent reconstructions of the user's competence.</Paragraph>
    <Paragraph position="2"> Does the large degree of inclusion of discourse models in user models at the level of content imply that the notion of discourse model is superflous? As was pointed out by Morik (this issue), extensionally overlapping notions may still prove useful if their intension highlights different aspects of a system. For example, in the above architecture, such a concept might characterize an orthogonal substructure and denote, for instance, entries in different partitions with specific origin or function. The above as well as Morik's and partly Wahlster's discussions demonstrate, however, that it is very hard to find such differential criteria for DMs. I therefore suspect that a happy fate of that kind will more probably apply to notions such as mentioned object memory or discourse sequence memory than to the vague notion of discourse model.</Paragraph>
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