1. College of Computer Science and Electronic Engineering, Hunan University, Changsha, Hunan, China
2. School of Graduate Studies, The City University of Hong Kong, Hong Kong
3. Computer Science and Engineering Department, The Chinese University of Hong Kong, Hong Kong
4. School of Computing Science, Simon Fraser University, Burnaby, Canada
5. Distributed Systems Group, Vienna University of Technology, Vienna, Austria
6. School of Computer Engineering, Nanyang Technological University, Singapore