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<Paper uid="C90-3098">
  <Title>USING THE SAME SYSTEM FOR ANALYZING AND SYNTHESIZING SENTENCES</Title>
  <Section position="4" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1. INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> The quality of a natural language interface must be estimated not only in terms of linguistic coverage but also in terms of procedures dealing with unexpected expressions (incorrect formulations or correct ones, not provided by the interface).</Paragraph>
    <Paragraph position="1"> Knowi_ng that error recovery is a complex task in the &amp;quot;restricted&amp;quot; framework of prograrruning languages (limited syntax and rlgourously defined semantics), one can appreciate the difficulty of endowing natural language interfaces with such capabilities. One can resort to flexible parsing for analysing &amp;quot;deviant&amp;quot; expressions typed by users \[Carbonell and Hayes 1983\], but this method can mislead them about the interface's real capabilities \[Mathieu and Sabatier 1986; S abatier 1987\].</Paragraph>
    <Paragraph position="2"> Our approach is quite different. We have developped a generator of natural language (French and English) interfaces to relational databases, Leader \[Benoit et al. 1988\]. An interesting characteristic is that our system can lead the user towards provided fommlations in a user-friendly way. The user can compose step by step questions by means of information dynamically synthesized by Leader. The same system with the same grammar is used both in analysis and synthesis. We specify in this paper the advantages of guided composition. We detail the problems we have encountered and we provide solutions for partial synthesis. We give the principles of the analysis-synthesis algorithm.</Paragraph>
  </Section>
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