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<Paper uid="P95-1010">
  <Title>Features and Agreement</Title>
  <Section position="6" start_page="73" end_page="75" type="concl">
    <SectionTitle>
5 Conclusion
</SectionTitle>
    <Paragraph position="0"> This paper has examined some of the differences between a standard complex feature-structure account of agreement, which is fundamentally organized around a notion of consistency, and an account in an extended version of LCG, in which agreement is fundamentally an asymmetric relationship.</Paragraph>
    <Paragraph position="1"> We have attempted to show that the LCG account of agreement correctly treats a number of cases of coordination which are problematic for the standard feature-based account. Although we have not shown this here, the LCG account extends straight-forwardly to the cases of coordination and morphological neutralization discussed by Zaenen and Kartunen (1984), Pullum and Zwicky (1986) and Ingria (1990).</Paragraph>
    <Paragraph position="2"> The nature of an appropriate feature system for LCG is still an open question. It is perhaps surprising that the simple feature system proposed here can handle such complex linguistic phenomena, but additional mechanisms might be required to treat other linguistic constructions. The standard account of adverbial modification in standard LCG, for instance, treat.~ adverbs as functors. Because the verb</Paragraph>
    <Paragraph position="4"> heading an adverbial modified VP agrees in number with its subject, the same number features will have to appear in both the antecedent and consequent of the adverb. Using the LCG account described above it is necessary to treat adverbs as ambiguous, assigning them to the categories (s\np^sg)\(s\np^sg) and</Paragraph>
    <Paragraph position="6"> There are several approaches which may eliminate the need for such systematic ambiguity. First, if the language of (category) types is extended to permit universally quantified types as suggested by Morrill (Morrill, 1992), then adverbs could be assigned to the single type VX.((s\np^X)\(s\np^X)).</Paragraph>
    <Paragraph position="7"> Second, it might be possible to reanalyse adjunction in such a way that avoids the problem altogether. For example, Bouma and van Noord (1994) show that assuming that heads subcategorize for adjuncts (rather than the other way around, as is standard) permits a particularly elegant account of the double infinitive construction in Dutch. If adjuncts in general are treated as arguments of the head, then the 'problem' of 'passing features' through adjunction disappears.</Paragraph>
    <Paragraph position="8"> The comparative computational complexity of both the unification-based approach and the LCG accounts is also of interest. Despite their simplicity, the computational complexity of the kinds of feature-structure and LCG grammars discussed here is largely unknown. Dorre et. al. (1992) showed that the satisfiability problem for systems of feature-structure subsumption and equality constraints is undecidable, but it is not clear if such problems can arise in the kinds of feature-structure grammars discussed above. Conversely, while terminating (Gentzen) proof procedures are available for extended LCG systems of the kind we presented here, none of these handle the coordination schema, and as far as we are aware the computational properties of systems which include this schema are largely unexplored.</Paragraph>
  </Section>
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