Affiliation: | 1 Department of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan 106, Republic of China Email: ktw@csie.ntu.edu.tw 2 Department of Computer Science and Information Engineering, National Chung Cheng University, Chiayi, Taiwan 621, Republic of China 3 Department of Computer Science, City University of Hong Kong, Kowloon, Hong Kong |