Abstract
The importance of document retrieval systems which can retrieve relevant documents for user's needs is now increasing with the growing availability of full-text documents. In the traditional document retrieval, each document is treated as a single unit. However, since long documents tend to contain various topics, the passage-level retrieval has been received more attention in the recent document retrieval. The passage can be considered as a sequent part of the document which contains a content related to a content of the query. In the passage retrieval, it is a problem how to decide the passages. It is considered that the passages which form coherent semantic units can effectively improve the accuracy. Furthermore, it may be also effective that the size and position of passage can be flexibly changed determining on the query and the document. In this paper, we describe a better method for calculating the passages that uses lexical chains. We will also present a passage-level document retrieval method which improves the accuracy.
