Preface

In the past few years, we have witnessed rapid proliferation of online social network services, such as Facebook, Twitter, and Del.icio.us, which greatly facilitate the collaboration, sharing, and other kinds of interactions among individuals. The term 'social media' has thus been coined to embrace all those new collaborative services or applications and also to indicate a new "social" approach to generating and distributing Web contents. The everincreasing social network services produce large-scale social data for analyzing user behaviors, and then improving existing services. On the other hand, they also bring forth more severe information overload and require more flexible and robust computing platforms or service paradigms.