Hybrid rule-based - example-based MT: feeding Apertium with sub-sentential translation units

This paper describes a hybrid machine translation (MT) approach that consists of integrating bilingual chunks (sub-sentential translation units) obtained from parallel corpora into an MT system built using the Apertium free/open-source rule-based machine translation platform, which uses a shallow-transfer translation approach. In the integration of bilingual chunks, special care has been taken so as not to break the application of the existing Apertium structural transfer rules, since this would increase the number of ungrammatical translations. The method consists of (i) the application of a dynamic-programming algorithm to compute the best translation coverage of the input sentence given the collection of bilingual chunks available; (ii) the translation of the input sentence as usual by Apertium; and (iii) the application of a language model to choose one of the possible translations for each of the bilingual chunks detected. Results are reported for the translation from English-to-Spanish, and vice versa, when marker-based bilingual chunks automatically obtained from parallel corpora are used.Generalitat Valenciana through grant BEST/2009/057. Spanish Ministry of Science and Innovation through project TIN2009-14009-C02-01. Science Foundation Ireland (SFI) through ETS Walton Award 07/W.1/I1802. Andy Way acknowledges support from SFI through grants 05/IN/1732 and 06/RF/CMS064