Exploiting morphology and local word reordering in English-to-Turkish Phrase-based statistical machine translation

I̊lknur Durgar El-Kahlout, Kemal Oflazer

Research output: Contribution to journalArticle

11 Citations (Scopus)


In this paper, we present the results of our work on the development of a phrase-based statistical machine translation prototype from English to Turkishan agglutinative language with very productive inflectional and derivational morphology. We experiment with different morpheme-level representations for EnglishTurkish parallel texts. Additionally, to help with word alignment, we experiment with local word reordering on the English side, to bring the word order of specific English prepositional phrases and auxiliary verb complexes, in line with the morpheme order of the corresponding case-marked nouns and complex verbs, on the Turkish side. To alleviate the dearth of the parallel data available, we also augment the training data with sentences just with content word roots obtained from the original training data to bias root word alignment, and with highly reliable phrase-pairs from an earlier corpus alignment. We use a morpheme-based language model in decoding and a word-based language model in re-ranking the n-best lists generated by the decoder. Lastly, we present a scheme for repairing the decoder output by correcting words which have incorrect morphological structure or which are out-of-vocabulary with respect to the training data and language model, to further improve the translations. We improve from 15.53 BLEU points for our word-based baseline model to 25.17 BLEU points for an improvement of 9.64 points or about 62% relative.

Original languageEnglish
Article number5272404
Pages (from-to)1313-1322
Number of pages10
JournalIEEE Transactions on Audio, Speech and Language Processing
Issue number6
Publication statusPublished - 2010
Externally publishedYes



  • Complex morphology
  • English
  • statistical machine translation (SMT)
  • Turkish
  • word reordering

ASJC Scopus subject areas

  • Acoustics and Ultrasonics
  • Electrical and Electronic Engineering

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