A Decoder for Syntax-based Statistical MT

This paper describes a decoding algorithm for a syntax-based translation model (Yamada and Knight, 2001). The model has been extended to incorporate phrasal translations as presented here. In contrast to a conventional word-to-word statistical model, a decoder for the syntaxbased model builds up an English parse tree given a sentence in a foreign language. As the model size becomes huge in a practical setting, and the decoder considers multiple syntactic structures for each word alignment, several pruning techniques are necessary. We tested our decoder in a Chinese-to-English translation system, and obtained better results than IBM Model 4. We also discuss issues concerning the relation between this decoder and a language model.