Effective Use of Dependency Structure for Bilingual Lexicon Creation

Existing dictionaries may be effectively enlarged by finding the translations of single words, using comparable corpora. The idea is based on the assumption that similar words have similar contexts across multiple languages. However, previous research suggests the use of a simple bag-of-words model to capture the lexical context, or assumes that sufficient context information can be captured by the successor and predecessor of the dependency tree. While the latter may be sufficient for a close language-pair, we observed that the method is insufficient if the languages differ significantly, as is the case for Japanese and English. Given a query word, our proposed method uses a statistical model to extract relevant words, which tend to co-occur in the same sentence; additionally our proposed method uses three statistical models to extract relevant predecessors, successors and siblings in the dependency tree. We then combine the information gained from the four statistical models, and compare this lexical-dependency information across English and Japanese to identify likely translation candidates. Experiments based on openly accessible comparable corpora verify that our proposed method can increase Top 1 accuracy statistically significantly by around 13 percent points to 53%, and Top 20 accuracy to 91%.