Head finalization: a simple reordering rule for SOV languages

  • Authors:
  • Hideki Isozaki;Katsuhito Sudoh;Hajime Tsukada;Kevin Duh

  • Affiliations:
  • NTT Corporation, Sorakugun, Kyoto, Japan;NTT Corporation, Sorakugun, Kyoto, Japan;NTT Corporation, Sorakugun, Kyoto, Japan;NTT Corporation, Sorakugun, Kyoto, Japan

  • Venue:
  • WMT '10 Proceedings of the Joint Fifth Workshop on Statistical Machine Translation and MetricsMATR
  • Year:
  • 2010

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Abstract

English is a typical SVO (Subject-Verb-Object) language, while Japanese is a typical SOV language. Conventional Statistical Machine Translation (SMT) systems work well within each of these language families. However, SMT-based translation from an SVO language to an SOV language does not work well because their word orders are completely different. Recently, a few groups have proposed rule-based preprocessing methods to mitigate this problem (Xu et al., 2009; Hong et al., 2009). These methods rewrite SVO sentences to derive more SOV-like sentences by using a set of handcrafted rules. In this paper, we propose an alternative single reordering rule: Head Finalization. This is a syntax-based preprocessing approach that offers the advantage of simplicity. We do not have to be concerned about part-of-speech tags or rule weights because the powerful Enju parser allows us to implement the rule at a general level. Our experiments show that its result, Head Final English (HFE), follows almost the same order as Japanese. We also show that this rule improves automatic evaluation scores.