1. Department of Computing, The Hong Kong Polytechnic University, Hong Kong, P. R. China
2. Department of Computer Science, City University of Hong Kong, Hong Kong, P. R. China
3. School of Computers, Guangdong University of Technology, Guangzhou, P. R. China
4. School of Software, Dalian University of Technology, Dalian, P. R. China
5. College of Computer Science, Sichuan University, Chengdu, P. R. China
6. School of Computer Science, The University of Sydney, NSW, Australia