Hua Luan received her M.S. degree from Shandong University. She is a Ph.D. candidate at Renmin University of China. Her research interests include databases and data warehouses. She is a student member of CCF.E-mail:luanhua@ruc.edu.cn Xiao-Yong Du received the Ph.D. degree from Nagoya Institute of Technology, Japan in 1997. He is a professor and doctoral supervisor at Renmin University of China. His research interests include high performance databases, intelligent information retrieval and semantic web. He is a member of CCF.E-mail:duyong@ruc.edu.cn Shan Wang received the M.S. degree in computer science from Renmin University of China in 1981. She is a professor and doctoral supervisor at Renmin University of China. Her research interests include high performance databases, knowledge systems, data warehouses and grid data management. She is a senior member of CCF and a member of ACM.E-mail:swang@ruc.edu.cn