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<Paper uid="C90-3080">
  <Title>QPATR and Constraint Threading</Title>
  <Section position="1" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
Abstract
QPATR is an MS-DOS Arity/PROLOG implemen-
</SectionTitle>
    <Paragraph position="0"> tation of the PATR-II formalism for unification grammar.</Paragraph>
    <Paragraph position="1"> The fbnnalism has been extended to include the constraints of LFG as well as negation and disjunction, which are implemented with the disjunction and negation-as-failure of PROLOG itself. A technique of constraint threading is employed to collect negative and constraining conditions in PROLOG difference lists. The parser of QPATR uses a left-corner algorithm for context-free grammars and includes a facility for identifying new lexical items in input on the basis of contextual information.</Paragraph>
  </Section>
class="xml-element"></Paper>