1. Department of Information Management and Finance, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan
2. Department of Computing, Coventry University, Priory Street, Coventry CV1 5FB, UK
3. Department of Management Information Systems, National Pingtung University of Science and Technology, 1 Shuefu Road, Neipu, Pingtung 912, Taiwan
4. Telecommunication Laboratories, Chunghwa Telecom Co., Ltd., 99 Dianyan Road, Yangmei District, Taoyuan 326, Taiwan
5. Department of Communication and Technology, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan
6. School of Computing and Information Systems, Athabasca University, 1 University Drive, Athabasca, AB, Canada T9S 3A3