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<Paper uid="P06-1023">
  <Title>Sydney, July 2006. c(c)2006 Association for Computational Linguistics Trace Prediction and Recovery With Unlexicalized PCFGs and Slash Features</Title>
  <Section position="2" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
Abstract
</SectionTitle>
    <Paragraph position="0"> This paper describes a parser which generates parse trees with empty elements in which traces and fillers are co-indexed.</Paragraph>
    <Paragraph position="1"> The parser is an unlexicalized PCFG parser which is guaranteed to return the most probable parse. The grammar is extracted from a version of the PENN treebank which was automatically annotated with features in the style of Klein and Manning (2003). The annotation includes GPSG-style slash features which link traces and fillers, and other features which improve the general parsing accuracy. In an evaluation on the PENN tree-bank (Marcus et al., 1993), the parser outperformed other unlexicalized PCFG parsers in terms of labeled bracketing fscore. Its results for the empty category prediction task and the trace-filler co-indexation task exceed all previously reported results with 84.1% and 77.4% fscore, respectively.</Paragraph>
  </Section>
class="xml-element"></Paper>