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<Paper uid="P93-1014">
  <Title>A UNIFICATION-BASED PARSER FOR RELATIONAL GRAMMAR</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> Although the impact of relational grammar (RG) on theoretical linguistics has been substantial, it has never previously been put in a form suitable for computational use. RG's multiple syntactic strata would seem to preclude its use in the kind of monotonic, unification-based parsing system many now consider standard (\[1\], \[11\]). However, recent work by Johnson and Moss \[2\] on a Kasper-Rounds (KR) style logic-based formalism \[5\] for RG, called Stratified Feature Grammar (S FG), has demonstrated that even RG's multiple strata are amenable to a feature-structure treatment. null Based on this work, we have developed a unification-based, chart parser for a lexical version of SFG suitable for building computational relational grammars. A lexicalized SFG is simply a collection of stratified feature graphs (Sgraphs), each of which is anchored to a lexical item, analogous to lexicalized TAGs \[10\]. The basic parsing operation of the system is S-graph unification (S-unification): This is essentially ordinary feature-structure unification augmented with an operation of label unification to build the stratified features characteristic of SFG.</Paragraph>
  </Section>
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