Adapted Seed Lexicon and Combined Bidirectional Similarity Measures for Translation Equivalent Extraction from Comparable Corpora

An improved method for extracting translation equivalents from bilingual comparable corpora according to contextual similarity was developed. This method has two main features. First, a seed bilingual lexicon—which is used to bridge contexts in different languages—is adapted to the corpora from which translation equivalents are to be extracted. Second, the contextual similarity is evaluated by using a combination of similarity measures defined in opposite directions. An experiment using Wall Street Journal and Nihon Keizai Shimbun corpora, together with the EDR bilingual dictionary, demonstrated that the method effectively improves the coverage of a bilingual lexicon; the accuracy of lists of candidate translation equivalents for frequently occurring unknown words was around 30%.