[1] Hong Kong University of Science and Technology, Hong Kong, Hong Kong
[2] Beijing Normal University, R and D Center for Knowledge Enginering, 100875, Beijing, China
[3] Simon Fraser University, School of Computing Science, Burnaby, BC V5A 1S6, Canada
[4] University of Porto, Faculty of Economics, 4200-465 Porto, Portugal
[5] Renmin University, School of Information, 100872 Beijing, China