Question Answering Experiments at NTCIR-5: Acquisition of Answer Evaluation Patterns and Context Processing using Passage Retrieval

In our participation in QAC3, our Question Answering system developed for QAC2 is extended in two ways, separately. The first system is constructed to improve the performance of answer evaluation. The automatic lexico-syntactic pattern acquisition from large corpora and the method to incorporate the patterns into QA system are developed and evaluated. The second system is constructed to implement the ability of context processing for information access dialogue (IAD), which is a main target ofQAC3 evaluation. The system exploits passage retrieval for selecting an appropriate context from the history of the series questions, in order to compose a complete question.