NTT System Description for the WMT2006 Shared Task

We present two translation systems experimented for the shared-task of "Workshop on Statistical Machine Translation," a phrase-based model and a hierarchical phrase-based model. The former uses a phrasal unit for translation, whereas the latter is conceptualized as a synchronous-CFG in which phrases are hierarchically combined using non-terminals. Experiments showed that the hierarchical phrase-based model performed very comparable to the phrase-based model. We also report a phrase/rule extraction technique differentiating tokenization of corpora.