1. Visiting Professor, Dept. of Computer Science, Stanford University, Stanford, CA 94305-9010, USA. yingxuw@stanford.edu
2. International Center for Cognitive Informatics (ICfCI), Theoretical and Empirical Software Engineering Research Centre (TESERC), Dept. of Electrical and Computer Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive, NW, Calgary, Alberta, Canada T2N 1N4. yingxu@ucalgary.ca