Automatic transliteration for Japanese-to-English text retrieval

For cross language information retrieval (CLIR) based on bilingual translation dictionaries, good performance depends upon lexical coverage in the dictionary. This is especially true for languages possessing few inter-language cognates, such as between Japanese and English. In this paper, we describe a method for automatically creating and validating candidate Japanese transliterated terms of English words. A phonetic English dictionary and a set of probabilistic mapping rules are used for automatically generating transliteration candidates. A monolingual Japanese corpus is then used for automatically validating the transliterated terms. We evaluate the usage of the extracted English-Japanese transliteration pairs with Japanese to English retrieval experiments over the CLEF bilingual test collections. The use of our automatically derived extension to a bilingual translation dictionary improves average precision, both before and after pseudo-relevance feedback, with gains ranging from 2.5% to 64.8%.