1. Department
of Information Systems and Mathematical Sciences, Nanzan University, Seto 489-0863, Japan
2. Graduate
School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan
3. RIKEN, Saitama 351-0198, Japan
4. Department
of Computer Science, Kyoto Sangyo University, Kyoto 603-8555, Japan
5. National Institute of Informatics, Tokyo 101-8430, Japan