Bi-directional Cross Language Question Answering using a Single Monolingual QA System

Toward the first attempt of evaluating Cross Lingual Question Answering in NTCIR workshop 5, our team participated in the English-Japanese subtasks of both directions (E-J and J-E tasks). Our approach to construct the CLQA systems of both directions is to use only a single (Japanese) QA system. Instead of CLIR systems, we also used statistical machine translation systems of both directions. For the Englishto-Japanese CLQA system, the straightforward cascade architecture, in which an E-J machine translation component is followed by a Japanese QA system, is augmented by the several supporting components that take advantage of original, therefore not degraded, information extracted from the question in English. For the Japanese-to-English CLQA system, the retrieved passages in English, which are relevant to the original Japanese question, are translated back to the passage in Japanese. Then the Japanese QA system is invoked by submitting the original Japanese question to extract the answer from the translated passages. The proposed method is effective for building a bi-directional CLQA system between the specific language pairs, in which only one language side has its monolingual QA system: this is often the case between a major language and a minor language.