1. School of Software Engineering, Faculty of Information Technology, Beijing University of Technology, Beijing, China
2. School of Automation Science and Electrical Engineering, Beihang University, Beijing, China
3. Cloud Computing and Distributed Systems Laboratory, School of Computing and Information Systems, University of Melbourne, Melbourne, VIC, Australia
4. CSSC Systems Engineering Research Institute, Beijing, China
5. Department of Computer Science, Southern Methodist University, Dallas, TX, USA
6. Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ, USA