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A Hybrid Approach for Automatic Extraction of Bilingual Multiword Expressions from Parallel Corpora

Specific-domain bilingual lexicons play an important role for domain adaptation in machine translation. The entries of these types of lexicons are mostly composed of MultiWord Expressions (MWEs). The manual construction of MWEs bilingual lexicons is costly and time-consuming. We often use word alignment approaches to automatically construct bilingual lexicons of MWEs from parallel corpora. We present in this paper a hybrid approach to extract and align MWEs from parallel corpora in a one-step process. We formalize the alignment process as an integer linear programming problem in order to find an approximated optimal solution. This process generates lists of MWEs with their translations, which are then filtered using linguistic patterns for the construction of the bilingual lexicons of MWEs. We evaluate the bilingual lexicons of MWEs produced by this approach using two methods: a manual evaluation of the alignment quality and an evaluation of the impact of this alignment on the translation quality of the phrase-based statistical machine translation system Moses. We experimentally show that the integration of the bilingual MWEs and their linguistic information into the translation model improves the performance of Moses.