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<Paper uid="P85-1028">
  <Title>Explana~..: 3tructures in XSEL</Title>
  <Section position="8" start_page="235" end_page="236" type="concl">
    <SectionTitle>
4. Rationale
</SectionTitle>
    <Paragraph position="0"> The knowledge structures just described, including mas=mge~ query.terms, the query-queue, schemas and links, serve as intermediate structures between the reasoning knowledge of the expert system and the linguistic knowledge needed for language generation .4 Some of the terminology used to describe these structures, e.g., &amp;quot;reason&amp;quot; and &amp;quot;elaboration&amp;quot; relations, is derived from the work of Mann \[7\] and Hobbs\[3\] on discourse organization. Mann and Hobbs independently postulate that discourse relations, such as reason and elaboration relations among others, are rasDonsible for coherence in well-organized  natural language text. One of the premises of this work on explanation generation is that the relations, or links, that are embodied in the inference rules of a successful reasoning system are the same ones that give coherence to natural language explanations. An immediate goal of this research is to identity those relations. At the present time only twenty.six different reasoning relations, have been identified in XSEL. As more types of reasoning relations are identified and corresponding links are added to XSEL's rules, more of XSEL's reasoning will be explainable. A long term goal of this work is to continue to identify and add reasoning links and schemas until we see some generalities begin to emerge. Perhaps some domain-independent set of reasoning relations and schemas might be found. Furthermore. such relations and schemas might facilitate the design of a knowledge acquisition system that would elicit knowledge from an expert, represent it as relations, and generate inference rules from relations. We realize that this could be a very long term goal, but it aJse has the short term benefit of providing useful explanations.</Paragraph>
    <Paragraph position="1"> 4~ ~ld~ \[91 for another ~ ot intermediate</Paragraph>
  </Section>
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