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<Paper uid="H05-1023">
  <Title>Proceedings of Human Language Technology Conference and Conference on Empirical Methods in Natural Language Processing (HLT/EMNLP), pages 177-184, Vancouver, October 2005. c(c)2005 Association for Computational Linguistics Inner-Outer Bracket Models for Word Alignment using Hidden Blocks</Title>
  <Section position="2" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
Abstract
</SectionTitle>
    <Paragraph position="0"> Most statistical translation systems are based on phrase translation pairs, or &amp;quot;blocks&amp;quot;, which are obtained mainly from word alignment. We use blocks to infer better word alignment and improved word alignment which, in turn, leads to better inference of blocks. We propose two new probabilistic models based on the inneroutersegmentationsanduseEMalgorithms null for estimating the models' parameters. The first model recovers IBM Model-1 as a special case. Both models outperform bi-directional IBM Model-4 in terms of word alignment accuracy by 10% absolute on the F-measure. Using blocks obtained from the models in actual translation systems yields statistically significant improvements in Chinese-English SMT evaluation.</Paragraph>
  </Section>
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