1. School of Computer Science, Nanjing University of Posts and Telecommunications, Nanjing, China
2. School of Managment, Hefei University of Technology, Hefei, China
3. Jiangsu Provincial Key Laboratory of E-Business, Nanjing University of Finance and Economics, Nanjing, China
4. School of Computing, Faculty of Science and Engineering, Macquarie University, Sydney, NSW, Australia
5. School of Computer Science, Nanjing Audit University, Nanjing, China