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<Paper uid="N06-1040">
  <Title>Probabilistic Context-Free Grammar Induction Based on Structural Zeros</Title>
  <Section position="1" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
Abstract
</SectionTitle>
    <Paragraph position="0"> We present a method for induction of concise and accurate probabilistic context-free grammars for efficient use in early stages of a multi-stage parsing technique.</Paragraph>
    <Paragraph position="1"> The method is based on the use of statistical tests to determine if a non-terminal combination is unobserved due to sparse data or hard syntactic constraints. Experimental results show that, using this method, high accuracies can be achieved with a non-terminal set that is orders of magnitude smaller than in typically induced probabilistic context-free grammars, leading to substantial speed-ups in parsing. The approach is further used in combination with an existing reranker to provide competitive WSJ parsing results.</Paragraph>
  </Section>
class="xml-element"></Paper>