Topic hierarchy in social networks

The increasing usage of on-line social networks has open new research areas such social network analysis. In this survey we review the literature and concepts around this topics with a special emphasis on the hierarchical representation of the graph structure of the social networks. There have been concepts and techniques, of data mining, social networks, and graphs, adapted to this context, taking into consideration that the community structure of a network can be defined as a dendrogram that shows how a network is organized from smaller communities at lower levels to larger ones at higher levels.