Document Structure Analysis for the NTCIR-5 Patent Retrieval Task

This paper describes our system participated in the Document and Passage Retrieval Subtasks at the NTCIR-5 Patent Retrieval Task. The purpose of these subtasks was the invalidity search, in which a patent application including a target claim is used to search documents that can invalidate the demand in the claim. Our system is characterized by the structure analysis for both target claim and entire application. The target claim is segmented into components, each of which is used to produce an initial query. The structure of the application is used to enhance each query. The candidates of relevant documents are retrieved and ranked on a component-by-component basis. The final document list is obtained by integrating these document lists. All passages in each document are ranked according to the relevance to the target claim. We show the effectiveness of our system experimentally.