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<Paper uid="A88-1017">
  <Title>Structure from Anarchy: Meta Level Representation of Expert System Propositions for Natural Language Interfaces. 1</Title>
  <Section position="2" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
1 Introduction
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    <Paragraph position="0"> A great deal of work has been done in constructing natural language interfaces to well structured underlying systems, such as data base systems. These natural language interfaces generally make use of an assumed system structure, such as a schema, to define semantics \[Martin, Appelt and Pereira 83; Grosz et. al. 85\] \[Woods et. al. 72; Woods 73\] \[Kaplan 79\]. On the other hand, almost no effort has been made in constructing natural language interfaces to systems that do not have such an extensive description, e.g. expert systems 2. The lack of such a schema means that the~ is no easy way to obtain information about propositions 3 of the underlying system. Thus, in order to build a natural  propositions. The terms pmlxmtion and fact an~ used interch~geably throughout thl. paper.</Paragraph>
    <Paragraph position="1"> language interface to expert systems the semantic interpreter must be able to provide the necessary structure. In an earlier paper \[Datskovsky Moerdler eLal. 87\] we briefly described a semantic interpreter that maps user statements into facts of an expert system, as well an inference engine for expert systems that can efficiendy utilize this input. In this paper we discuss the meta level description of the expert system propositions, similar to a schema of a data base, utilized by the semantic interpreter and show how this structure is used in processing of user questions.</Paragraph>
    <Paragraph position="2"> Our structure consists of a group of hierarchies which are formed from verb categories. The hierarchies provide a grouping of the propositions of an expert system by topic. For example, all propositions that deal with interpersonal relationships are grouped under one hierarchy, while those dealing with transfer of possession are grouped under another. The meaning of a proposition is specified step by step, as the hierarchy is traversed, thus allowing for mapping of various sentences, or parts of sentences into the propositions. To test our theories, the approach is currendy being implemented as a front end to a small expert system that deals with personal income tax matters 4.</Paragraph>
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