Syntax Augmented Machine Translation via Chart Parsing with Integrated Language Modeling

We present a hierarchical phrase-based translation model which annotates and generalizes existing phrase translations with syntactic categories derived from parsing the target side of a parallel corpus. We associate target parse trees for each training sentence pair with a search lattice constructed from the existing phrase translations on the corresponding source sentence, and consider techniques to produce a syntactically motivated bilingual synchronous grammar. We describe refinements to a chart based decoder and k-best extraction techniques to effectively parse the resulting grammar, which contains up to 4000 syntax-derivated nonterminals, producing translations that achieve significant improvements over Pharaoh, a stateof-the-art phrase based system, on the Europarl French-to-English task (Koehn and Monz, 2005).