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<Paper uid="P93-1044">
  <Title>Guiding an HPSG Parser using Semantic and Pragmatic Expectations</Title>
  <Section position="7" start_page="296" end_page="296" type="concl">
    <SectionTitle>
SUMMARY
</SectionTitle>
    <Paragraph position="0"> Pragmatic knowledge about language usage in routine conversational contexts can be highly compiled. This knowledge can be used to produce semantic and syntactic expectations about next turns in conversation, especially of next turns that are second members of adjacency pairs (Schegloff &amp; Sacks 1973). By mapping expected features into HPSG constraints, and by augmenting HPSG sign structures to model the role structure of systemic grammar, these expectations can be used as constraints on possible constituent structures of a HPSG constituent. Given this mapping, the expectations may then be used to order the parse process, guiding the parse, and avoiding the consideration of pragmatically unlikely constructions. This process reduces the number of constituents considered during parsing, reducing parse time and permitting the parser to correctly select the parse most like the pragmatic expectations, This solution closely follows a classical A.I. search technique called a best-first search. The heuristic evaluation function used to classify the proposed constituents for best first ordering uses inference similar to abductive reasoning.</Paragraph>
    <Paragraph position="1"> One benefit of this solution is that it retains the modularity of the syntactic and semantic components, not requiring a specialized grammar for each contextual domain. In additional, as the coverage of the grammar increases, the search space will also increase, and thus possible benefits increase.</Paragraph>
    <Paragraph position="2"> Work is continuing on this study. Currently the heuristic is being enhanced to consider the specificity of an expectation match, ordering those edges which match the most specific features first. In addition, work is in progress to extend the coverage of the grammar and mapping to include the conversation domain utilized in Patten, Geis &amp; Becker 1992.</Paragraph>
  </Section>
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