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<Paper uid="P98-1115">
  <Title>Compacting the Penn Treebank Grammar</Title>
  <Section position="9" start_page="699" end_page="702" type="concl">
    <SectionTitle>
PTB II;
</SectionTitle>
    <Paragraph position="0"> * the analysis of the source of this continued growth in terms of partial bracketting and the justification this provides for compaction via rule-parsing; * the result that the compacted rule set does approach a limit at some point dur- null ing staged rule extraction and compaction, after a sufficient amount of input has been processed; * that, though the fully compacted grammar produces lower parsing performance than the extracted grammar, a 58% reduction (without loss) can still be achieved by using linguistic compaction, and 69% reduction yields a gain in recall, but a loss in precision.</Paragraph>
    <Paragraph position="1"> The latter result in particular provides further support for the possible future utility of the compaction algorithm. Our method is similar to that used by Shirai (Shirai et al., 1995), but the principal differences are as follows. First, their algorithm does not employ full context-free parsing in determining the redundancy of rules, considering instead only direct composition of the rules (so that only parses of depth 2 are addressed). We proved that the result of compaction is independent of the order in which the rules in the grammar are parsed in those cases involving 'mutual parsability' (discussed in Section 4), but Shirai's algorithm will eliminate both rules so that coverage is lost. Secondly, it is not clear that compaction will work in the same way for English as it did for Japanese.</Paragraph>
  </Section>
class="xml-element"></Paper>