1. S/W Group, Computer and Information R&D Center, Samsung Electronics Co. Ltd., P.O. Box 105, Suwon, Kyungki-Do 449–900, Republic of Korea
2. Department of Computer Science and Center for AI Research, Korea Advanced Institute of Science and Technology, 373–1, Kusung-Dong, Yusung-Gu, Taejon 305–701, Republic of Korea