I. INTRODUCTION
Personal social networks are big and cluttered, yet contain
highly valuable information [1]. Taking Facebook along, as of
2014, its market value already exceeds 156 billion US dollar.
Organizing users’ friends into circles or communities is a
fundamental task in social network research [2][3]. Social
network sites like Facebook and Twitter allow users to
manually categorize their friends into social circles, but this
process is laborious, error-prone and inadaptable to changes.