document: On the high density of leadership nuclei in endorsement social networks In this paper we study the community structure of endorsement networks , i.e. , social networks in which a directed edge u → v is asserting an action of support from user u to user v. Examples include scenarios in which a user u is favoring a photo , liking a post , or following the microblog of user v. Starting from the hypothesis that the footprint of a community in an endorsement network is a bipartite directed clique from a set of followers to a set of leaders , we apply frequent itemset mining techniques to discover such bicliques . Our analysis of real networks discovers that an interesting phenomenon is taking place : the leaders of a community are endorsing each other forming a very dense nucleus .
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