An Optimized Query Evaluation in a Hierarchical Mediator System

Kil Hong Joo: Department of Computer Education, Gyeongin National University of Education, Incheon, Korea (TEL) +82-32-540-1283 (E-Mail) khjoo@ginue.ac.kr

Jaeho Lee: Department of Computer Education, Gyeongin National University of Education, Incheon, Korea (TEL) +82-32-540-1281 (E-Mail) jhlee@ginue.ac.kr

Jin Tak Choi: Department of Computer Science, Incheon University, Incheon, Korea (TEL) +82-32-770-8493 (E-Mail) choi@incheon.ac.kr

Jinsong Ouyang: Department of Computer Science, CSU Sacramento, USA (TEL) +1-916-278-7906 (E-Mail) ouyangj@ecs.csus.edu

Abstract

Recent research which purports to integrate distributed information has been concentrated on developing an efficient mediator that provides a high degree of autonomy for a local user. In a mediator that integrates several information sources, a global query can be transformed into a set of sub-queries and each sub-query is a unit of evaluation in its corresponding information source. The distributed mediators that include diverse information sources have made a hierarchy structure. In a hierarchical mediator system composed of semantically related mediators, a view in a mediator can be defined by views in other mediators, so that a sub-query in a mediator may need to be evaluated by a chain of other mediators. Due to this reason, such materialization can be much more effective. This paper proposes an algorithm for selecting the optimized set of sub-queries to be materialized in each mediator of a hierarchical mediator system adaptively such that the overall query evaluation cost of the hierarchical mediator system can be minimized at all times.

Short Biography

Kil Hong Joo: Kil Hong Joo is a Professor in the Department of Computer Education at Gyeongin National University of Education. His current research interests are in distributed database, integrated systems, mediator system, data mining, computer education, ubiquitous computing and e-learning.

Before he joined the faculty of Gyeongin National University of Education in 2005, he was a Plural Professor in the Department of Computer Science at HanSung Digital University from 2004 to 2005 and a research staff at the Yonsei Proteom Research Center from 2000 to 2004. He received a BS degree from the Department of Computer Science, Incheon University, in 1998; an MS degree from the Department of Computer Science, Yonsei University, in 2000; and a Ph.D degree from the Department of Computer Science, the Yonsei University, in 2004.

Jaeho Lee: Jaeho Lee is a Professor in the Department of Computer Education at Gyeongin National University of Education. His current research interests are in distributed database, data mining, computer education, ubiquitous computing and e-learning.

Before he joined the faculty of Gyeongin National University of Education in 1996, he was a senior research staff at the Electronic Telecommunications Research Institute from 1996 to 1989. He received a BS degree from the Department of Computer Science, Hong-ik University, in 1987; an MS degree from the Department of Computer Science, Hong-ik University, in 1989; and a Ph.D degree from the Department of Computer Science, the Hong-ik University, in 1996.

Jin Tak Choi: Jin Tak Choi is a Professor in the Department of Computer Science at Incheon University. His current research interests are in database, data protection, cryptography, and database protection.

Before he joined the faculty of Incheon University in 1987, he was an instructor in the Department of Computer Science at Incheon University from 1983 to 1987. He received a BS degree from the Department of Mathematics, Dong-kuk University, in 1977; an MS degree from the Department of Computer Science, Dong-kuk University, in 1982; and a Ph.D degree from the Department of Electronics Engineering, the Kyung-hee University, in 1991.

Jinsong Ouyang: Jinsong Ouyang is a Professor in the Department of Computer Science at CSU. His current research interests are in distributed and networking systems, security of distributed, networking, and embedded systems.