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<Paper uid="J02-3005">
  <Title>c(c) 2002 Association for Computational Linguistics Squibs and Discussions A Note on Typing Feature Structures</Title>
  <Section position="7" start_page="396" end_page="396" type="concl">
    <SectionTitle>
5. Further Research
</SectionTitle>
    <Paragraph position="0"> We have described in this article a method for validating the consistency of feature structure specifications in grammars that incorporate untyped feature structures. Although the use of feature structures in XTAG is very limited, especially since all feature structures are finitely bounded, the method we describe is applicable to feature structure-based grammatical formalisms in general; in particular, it will be interesting to test it on broad-coverage grammars that are based on unbounded feature structures, such as lexical functional grammars.</Paragraph>
    <Paragraph position="1"> We have applied type inference only statically; feature structures that are created at parse time are not validated. By modifying the unification algorithm currently used in XTAG, however, it is possible to use TFSs in the grammar and apply type inference at run time. This will enable detection of more errors at run time and provide for better representation of feature structures and possibly for more efficient unifications.</Paragraph>
    <Paragraph position="2"> In a new implementation of XTAG (Sarkar 2000), feature structure specifications are not evaluated as structures are being constructed; rather, they are deferred to the final stage of processing, when only valid trees remain. We plan to apply type inference to the resulting feature structures in this implementation, so that run-time errors can be detected as well.</Paragraph>
  </Section>
class="xml-element"></Paper>