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<Paper uid="J97-4003">
  <Title>A Computational Treatment of Lexical Rules in HPSG as Covariation in Lexical Entries</Title>
  <Section position="8" start_page="564" end_page="564" type="concl">
    <SectionTitle>
8. Summary
</SectionTitle>
    <Paragraph position="0"> We presented a new computational treatment of HPSG lexical rules by describing a compiler that translates a set of lexical rules as specifed by a linguist into definite relations, which are used to constrain lexical entries. The frame of a lexical rule and lexical rule interaction is automatically determined and the interaction is represented as a finite-state automaton. The automaton allows us to encode lexical rule interaction without actually having to apply lexical rules a possibly infinite number of times.</Paragraph>
    <Paragraph position="1"> Word classes relevant to lexical rule application are automatically detected and the corresponding finite-state automata are refined in order to avoid lexical rule applications that are guaranteed to fail. The refined automata are encoded as definite relations and each base lexical entry is extended to call the relation corresponding to its class.</Paragraph>
    <Paragraph position="2"> Finally, the encoding of lexical rules and their interaction is advanced using constraint propagation to allow coroutining of its execution with other grammar constraints. This reduces the number of nondeterministic choices related to lexical lookup, and, more importantly, allows syntactic information to be used to ensure termination of the covariation encoding of lexical rules. Finally, we discussed implementation results and illustrated the improvement in time and space efficiency resulting from the covariation encoding.</Paragraph>
  </Section>
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