关键词: 关系数据库，细粒度访问控制，查询改写，冗余

Abstract: Fine-grained access control has received much attention from research community due to the requirements of privacy preserving and Web-based applications. It is a promising approach to implement fine-grained access control by query modification. However, in the areing query modification algorithm, the features of the queries issued by users and the features of FGAC policy are not considered. Thus,there are redundancies in the final executed queries which make unnecessary overhead. We first analyzed two different redundancies bases on the feature of queries issued by users and the FGAC policies. I}hen, we proposed a technique to detect these redundancies and provided a new algorithm to implement FGAC. A comprehensive set of experiments show that the performance is improved by the proposed algorithm.

Key words: Relational database, Fine-grained access control, Query modification, Redundancy