1. Information Systems Architecture Research Division, National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda City, Tokyo 101-8430, Japan
2. Department of Electrical and Computer Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya Ward, Yokohama 240-8501, Japan
3. Graduate School of Environment and Information Sciences, Yokohama National University, 79-5 Tokiwadai, Hodogaya Ward, Yokohama 240-8501, Japan