Answer extraction based on query expansion in Chinese question answering system

When using natural language question to retrieval document, query expansion are the key factors that affect its retrieval performance. By analyzing the traditional query expansion method, this paper puts forward a query expansion method based on set theory for answering document retrieval. In order to verify the validity of the method, a similarity calculation method for question and candidate answer sentences is proposed to extract the answer. The major query expansion terms and the minor query expansion terms are taken into consideration with different weight in the similarity calculation. The experiment results show that the performance makes substantial improvement.