Jorng-Tzong Horng*, Ying-Ping Chen+ and Cheng-Yan Kao++
*Department of Computer Science and Information Engineering
National Central University
Chungli, Taoyuan, Taiwan 320, R.O.C.
E-mail: horng@db.csie.ncu.edu.tw
+Department of Computer Science and Information Engineering
University of Illinois
Urbana-Champaign, Illinois, U.S.A.
E-mail: ypchen@csie.ntu.edu.tw
++Department of Computer Science and Information Engineering
National Taiwan University
Taipei, Taiwan 106, R.O.C.
E-mail: cykao@csie.ntu.edu.tw