The Impact of Source–Side Syntactic Reordering on Hierarchical Phrase-based SMT

Syntactic reordering has been demon-strated to be helpful and effective for han-dling different word orders between source and target languages in SMT. However, in terms of hierarchial PB-SMT (HPB), does the syntactic reordering still has a signif-icant impact on its performance? This paper introduces a reordering approach which explores the { (DE) grammati-cal structure in Chinese. We employ the Stanford DE classifier to recognise the DE structures in both training and test sentences of Chinese, and then per-form word reordering to make the Chi-nese sentences better match the word or-der of English. The annotated and re-ordered training data and test data are ap-plied to a re-implemented HPB system and the impact of the DE construction is ex-amined. The experiments are conducted on the NIST 2008 evaluation data and ex-perimental results show that the BLEU and METEOR scores are significantly im-proved by 1.83/8.91 and 1.17/2.73 abso-lute/relative points respectively.