1. Institute of Information Science, Academia Sinica, Taipei, Taiwan
2. Department of Statistics and Information Science, College of Mathematics and Physics, Wenzhou University, Wenzhou, China
3. Institute of Information Science and the Research Center for Information Technology Innovation, Academia Sinica, Taipei, Taiwan
4. Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA
5. Department of Computer Science, National Tsing Hua University, Hsinchu, Taiwan