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<Paper uid="P01-1054">
  <Title>Tractability and Structural Closures in Attribute Logic Type Signatures</Title>
  <Section position="7" start_page="2" end_page="2" type="concl">
    <SectionTitle>
5 Conclusion
</SectionTitle>
    <Paragraph position="0"> Efficient compilation of both meet-semi-latticehood and subtype covering depends crucially in practice on sparseness, either of consistency among types, or of deranged types, to the extent it is possible at all. Closure for unique feature introduction runs in linear time in both the number of features and types. Subtype covering results in NP-complete non-disjunctive type inferencing, but the postponement of these constraints using constraint handling rules can often hide that complexity in the presence of other principles of grammar.</Paragraph>
  </Section>
class="xml-element"></Paper>