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<Paper uid="J88-3014">
  <Title>DISTINGUISHING USER MODELS FROM DISCOURSE MODELS</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> In the discussion about the relationship between user models (UMs) and discourse models (DMs) so far, at least three positions have been stated explicitly:  Of course, the interpretation of these positions depends on the definition of the terms involved and the underlying notion of the &amp;quot;part-of&amp;quot;, &amp;quot;intersect&amp;quot;, and &amp;quot;distinct&amp;quot; relations. The relationships cannot simply be interpreted in a set-theoretic sense, since all definitions for UMs and DMs proposed so far depend not only on representation structures, but also on processes used for the construction, maintenance, and exploitation of these structures.</Paragraph>
    <Paragraph position="1"> Since this is a terminological, and not an empirical, discussion, as I pointed out in Wahlster (1986), P1-P3 are primarily normative statements. So, P3, for instance, must be interpreted as &amp;quot;The terms UM and DM should be defined in such a way, that they do not overlap&amp;quot;.</Paragraph>
    <Paragraph position="2"> This view seems not to be shared by all participants in the discussion. Schuster, for example, tries to prove her position (PI) in a set-theoretic sense. First, she argues that &amp;quot;the user model contains information that does not appear in the discourse model&amp;quot; and then she &amp;quot;proves&amp;quot; that &amp;quot;any information in the discourse model is also in the user model&amp;quot;.</Paragraph>
    <Paragraph position="3"> I disagree not only with the form, but also with the content of Schuster's argumentation. She writes &amp;quot;only if the discourse model is part of the user model can the system take it into account in its responses and its reasoning about the users&amp;quot;. By considering an isomorphic argumentation like &amp;quot;only if a tomato is part of cheese, can one use it to prepare pizza&amp;quot; it becomes clear that this proof is flawed.</Paragraph>
    <Paragraph position="4"> Also, Morik points out correctly that if one follows Schuster's argumentation one should &amp;quot;view the grammar as part of the user model, because the grammar is necessary for understanding and producing utterances&amp;quot;. null Today, it is a standard hypothesis in AI and computational linguistics that models for the language understanding and generation process must exploit various knowledge sources, including in many cases a DM and a UM. For example, in Jameson and Wahlster (1982) we described the NP generator of the HAM-ANS system, in which the generation of a definite or indefinite description was influenced both by the UM and the DM.</Paragraph>
    <Paragraph position="5"> But this in no way means that one must be included in the other.</Paragraph>
    <Paragraph position="6"> As long as there is no definitive evidence (e.g., from psychology or the neurosciences) for a particular structure, content, and use (or even existence) of UMs and DMs in the human information processing system, in AI the notions of UM and DM are concepts that help on the one hand to construct a theory of natural language dialog behavior, and on the other hand to structure the software systems that realize natural language systems.</Paragraph>
    <Paragraph position="7"> From the second point of view, which is the engineering perspective, the question of whether P1, P2, or P3 holds, is easy to decide so far. In most of the implemented systems the data structures and procedures labeled UM and DM are completely distinct.</Paragraph>
    <Paragraph position="8"> Even the recent GUMS package (Finin 1988), a general user modeling component, contains no specific representation structures or processes for discourse modeling. null Since the discussion above suggests that we view the relation between the UM and the DM mainly as a terminological problem, in the next section we focus on possible definitions for UMs and DMs. Although often terminological discussions become quite tedious, at this point it seems to be important to define these concepts as precisely as possible, since many researchers are discovering interesting relationships between discourse and user models.</Paragraph>
    <Paragraph position="9"> Copyright 1988 by the Association for Computational Linguistics. Permission to copy without fee all or part of this material is granted provided that the copies are not made for direct commercial advantage and the CL reference and this copyright notice are included on the first page. To copy otherwise, or to republish, requires a fee and/or specific permission.</Paragraph>
  </Section>
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