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<Paper uid="P93-1014">
  <Title>A UNIFICATION-BASED PARSER FOR RELATIONAL GRAMMAR</Title>
  <Section position="9" start_page="102" end_page="103" type="concl">
    <SectionTitle>
CONCLUDING REMARKS
</SectionTitle>
    <Paragraph position="0"> The algorithm described above is simpler than the one we have implemented in a number of ways.</Paragraph>
    <Paragraph position="1"> We end by briefly mentioning some aspects of the  general algorithm.</Paragraph>
    <Paragraph position="2"> Optional Arcs: On encountering an optional arc, the parser considers two paths, skipping the optional arc on one and attempting to complete it on the other.</Paragraph>
    <Paragraph position="3"> Constraint Arcs These are reminiscent of LFG constraint equations. For a parse to be good, each constraint arc must unify with a structural arc.</Paragraph>
    <Paragraph position="4"> Multi-tiered S-graphs: These are S-graphs having a non-terminal incomplete arc I (e.g., the \[LOC\] arc in Figure 8. Essentially, the parser searches I depth-first for incomplete terminal arcs to complete.</Paragraph>
    <Paragraph position="5"> Pseudo-R-signs: These are names of sets of R-signs. For a parse to be good, each pseudo-Rsign must unify with a member of the set it names. Extractions: Our approach is novel: it uses pseudo-R-signs and multirooted S-graphs, illustrated in Figure 9, where p is the primary root and d, the dangling root, is the source of a &amp;quot;slashed arc&amp;quot; with label of the form (b,/\] (b a pseudo-R-sign). Since well-formed final parses must be  single-rooted, slashed arcs must eventually unify with another arc.</Paragraph>
    <Paragraph position="6"> To sum up: We have developed a unificationbased, chart parser for relational grammars based on the SFG formalism presented by Johnson and Moss \[2\]. The system involves compiling (combinations) of rules graphs and their associated lexical anchors into a lexicalized grammar, which can then be parsed in the same spirit as lexicalized TAGs. Note, though, that SFG does not use an adjunction (or substitution) operation.</Paragraph>
  </Section>
class="xml-element"></Paper>