Social networks use multiple data sources to identify people and their relationships. For example, a user-user connection graph shows connections that users have created on the network, a user-person invitation graph shows a mixture of user-user connections and user-email connections, and address book data provides a user-email graph.
The administrator of a social network who wants to know who has multiple accounts on the network can use the nTree function to generate a tree for every account and then compare these trees to find those that are likely to have the same person as the root node.