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<Paper uid="C00-2123">
  <Title>Word Re-ordering and DP-based Search in Statistical Machine Translation</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> The goal of machine translation is tile translation of a text given in some source language into a targel: language. We are given a source string fJ = fl ...fj.-.f.l of length J, wlfich is to be translated into a target string c\[ = cl ...ei...el of length I. Among all possible target strings, we will choose the string with the highest probability:</Paragraph>
    <Paragraph position="2"> The argmax operation denotes the search problem, i.e. the generation of the output sentence in the target language. Pr(c~) is the language model of tim target language, whereas Pr(fi'le*l) is the translation model. Our approach uses word-to-word dependencies between source and target words. The model is often further restricted so that each source word is assigned to exactly one target word (Brown et al., 1993; Ney et al., 2000). These alignment models are similar to the concept of hidden Markov models (HMM) in speech recognition. The alignment mapping is j --+ i = aj from source position j to target position i = aj. The use of this alignment model raises major problems if a source word has to be aligned to several target words, e.g. when translating German compound nouns. A siuLple extension will be used to handle this problem.</Paragraph>
    <Paragraph position="3"> In Section 2, we briefly review our approach to statistical machine translation. In Section 3, we introduce our novel concept to word re-ordering and a DP-based search, which is especially suitable for the translation direction fl'om German to English.</Paragraph>
    <Paragraph position="4"> This approach is compared to another re-ordering scheme presented in (Berger et al., 1996). In Section 4, we present the t)erformance measures used and give translation results on the Verbmobil task.</Paragraph>
  </Section>
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