1. Department of Computer Science and Intelligent Systems, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho Naka-ku, Sakai-Shi, Osaka 599-8531, Japan
2. Department of Artificial Intelligence, Faculty of Computer Science and Information Technology, University of Malaya, 50603 Kuala Lumpur, Malaysia
3. Department of Informatics, Faculty of Mathematics, Computer Science and Natural Sciences, University of Hamburg, Vogt-Koelln-Str. 30, 22527 Hamburg, Germany