In a system, a similarity based clustering algorithm is executed to generate clusters of user profiles. Each cluster includes a group of users in an electronic community. Each cluster represents a relationship between the users in each group that each cluster includes. Each cluster is stored in a user profile and relationship database. The similarity based clustering algorithm includes s a member importance function and a member similarity function. The member importance function ascertains an importance value of keywords as a depth of the keywords in a semantic hierarchical tree. The member similarity function ascertains a similarity distance between keywords as a path distance between the keywords in the semantic hierarchical tree. Executing the similarity based clustering algorithm includes: using the member importance function and the member similarity function to ascertain the clusters.