Integrated Use of Internal and External Evidence in the Alignment of Multi-Word Named Entities

This paper proposes a method of extracting English multi-word named entities and their Japanese equivalents from a parallel corpus. The aim of our research is to extract multi-word named entities which are not listed in a dictionary of an English-to-Japanese MT system and appear infrequently in a parallel corpus. Our method makes its alignment on the basis of two kinds of external evidence provided by the context in which a bilingual pair appears, as well as two kinds of internal evidence within the pair. Each evidence is accompanied by a score, and the aggregate score is computed as a weighted sum of the scores. The appropriate weights are estimated with the logistic regression analysis. An experiment using a parallel corpus of Yomiuri Shimbun and The Daily Yomiuri satisfactorily found that 86.36% of the extracted bilingual pairs with the highest scores were judged to be correct.