Improving English-Spanish statistical machine translation: experiments in domain adaptation, sentence paraphrasing, tokenization, and recasing

  • Authors:

  • Preslav Nakov

  • Affiliations:

  • University of California at Berkeley, Berkeley, CA

  • Venue:
  • StatMT '08 Proceedings of the Third Workshop on Statistical Machine Translation
  • Year:
  • 2008

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Abstract

We describe the experiments of the UC Berkeley team on improving English-Spanish machine translation of news text, as part of the WMT'08 Shared Translation Task. We experiment with domain adaptation, combining a small in-domain news bi-text and a large out-of-domain one from the Europarl corpus, building two separate phrase translation models and two separate language models. We further add a third phrase translation model trained on a version of the news bi-text augmented with monolingual sentence-level syntactic paraphrases on the source-language side, and we combine all models in a log-linear model using minimum error rate training. Finally, we experiment with different tokenization and recasing rules, achieving 35.09% Bleu score on the WMT'07 news test data when translating from English to Spanish, which is a sizable improvement over the highest Bleu score achieved on that dataset at WMT'07: 33.10% (in fact, by our system). On the WMT'08 English to Spanish news translation, we achieve 21.92%, which makes our team the second best on Bleu score.