Factoring Adjunction in Hierarchical Phrase-Based SMT

While much work has been done to inform Hierarchical Phrase-Based SMT (Chiang, 2005) models linguistically, the adjunct/argument distinction has generally not been exploited for these models. But as Shieber (2007) points out, capturing this distinction allows to abstract over ‘intervening’ adjuncts, and is thus relevant for (machine) translation in general. We contribute an adjunction-driven approach to hierarchical phrase-based modelling that uses source-side adjuncts to relax extraction constraints–allowing to capturing long-distance dependencies–, and to guide translation through labelling. The labelling scheme can be reduced to two adjunct/non-adjunct labels, and improves translation over Hiero by up to 0.6 BLEU points for English-Chinese.