Acknowledgements
We would like to thank all of the authors in this special issue for their great contributions and efforts to collaborate with us following a very tight publishing schedule. Forty reviewers provided constructive and valuable suggestions and comments for the submitted papers. This special issue and the 2012 AAG organized paper sessions are supported by the National Science Foundation under Grant No. 1028177, with the project titled “CDI-Type II: Mapping Cyberspace to Realspace: Visualizing and Understanding the Spatiotemporal Dynamics of Global Diffusion of Ideas and the Semantic Web”. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.