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<Paper uid="J88-3012">
  <Title>DISCOURSE MODELS~ DIALOG MEMORIES~ AND USER MODELS</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
2 DIALOG MEMORY AS PART OF USER MODEL
</SectionTitle>
    <Paragraph position="0"> A dialog memory can be viewed as part of a user model, namely the part that represents the dialog-dependent knowledge of the user (Morik 1984). Entries out of the dialog memory may cause entries in the user model, and entries of the user model may support the interpretation of an utterance, the interpretation then being stored in the dialog memory. However, in order to keep technical terms precise, user modeling on the one hand, and building and exploiting a dialog memory on the other hand should not be identified. This would lead to a reduction of what user modeling is about by disregarding all aspects other than dialog-dependent knowledge of the user as known to the system, while in fact there is some information that is to be covered by a user model and that may not be covered by a dialog memory.</Paragraph>
    <Paragraph position="1"> Let us think, for example, of a visit to the dentist's.</Paragraph>
    <Paragraph position="2"> The dentist will have some expectations concerning the client before the client said a word---even before he opened his mouth. This is due to the conversational setting, the roles of dentist and client. The same two persons meeting in another environment (e.g., at a political event, a horse race, or the opera) would not rely on the dentist-client expectations but on the information that then belongs to their roles.</Paragraph>
    <Paragraph position="3"> A user model contains explicit assumptions on the role of the user and the way a particular user plays it.</Paragraph>
    <Paragraph position="4"> The system exploits the user model systematically for playing its role more cooperatively by adopting to diverse users. To that end it uses rules which are parametrized according to the facets of the user. A user model is built up based on a &amp;quot;naive psychology&amp;quot;, which forms a consistent image of the user.</Paragraph>
    <Paragraph position="5"> Schuster also states that the user model covers entities that do not belong into the dialog memory. In addition to the argument mentioned above (the dialog memory being the part of the user model that represents the dialog-dependent knowledge of the user), she points out that the dialog memory is used for building up parts of the user model and that both, user model and dialog memory, are used for generating an adequate answer.</Paragraph>
    <Paragraph position="6"> But if this were a valid argument for establishing a subsumption relation, we should also view the grammar as part of the user model, because the grammar is necessary for understanding and producing utterances.</Paragraph>
    <Paragraph position="7"> All the knowledge sources of a natural language system (hopefully) work together. We separate them conceptually not because of their independence, but because they contain different kinds of knowledge that contribute to the overall task in different ways.</Paragraph>
    <Paragraph position="8"> A dialog memory contains all beliefs that can be inferred with certainty from utterances, so that they belong to the mutual belief space. For example, the objects and their properties introduced in a dialog are typical entries in a dialog memory. Also, presuppositions that can be inferred from articles or question particles belong into the dialog memory. The linguistic rules that determine the inferences are valid and binding for all conversational settings. General rules establish mutual beliefs on the basis of utterances. The dialog memory is then used for, e.g., determining the appro-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. 0362-613X/88/0100o-o$03.00 Computational Linguistics, Volume 14, Number 3, September 1988 95 Katharine Morik Discourse Models, Dialog Memories, and User Models priate description (definite/indefinite), anaphoric expression, or characterization.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="0" type="metho">
    <SectionTitle>
3 DIALOG MEMORY AS PART OF DISCOURSE MODEL
</SectionTitle>
    <Paragraph position="0"> Another notion that is very close to user model as well as to dialog memory is discourse model. Sometimes dialog memory and discourse model are treated as synonyms (e.g., Wahlster 1986). Given the above definition of dialog memories, however, there is a difference between the two notions. As opposed to Schuster, who defines a discourse model as &amp;quot;containing representations of entities, along with their properties and relations they participate in&amp;quot;, which corresponds exactly to our dialog memory, I use discourse model according to the framework of Grosz and Sidner (1986), where a discourse model is the syntactic structure of a dialog.</Paragraph>
    <Paragraph position="1"> One part of it, though, could be identified with the dialog memory, namely the focus space stack. The overall discourse model additionally represents the structure of the dialog with the segments and their relations, which is not part of the user model. Decomposing a dialog into segments and establishing relations between them does not depend on a particular conversational setting. As is the case with dialog memories the overall discourse model, too, is built up by general linguistic rules that need not be parametrized according to a certain user.</Paragraph>
  </Section>
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