A method for matching a user to a conversation includes, for each of a plurality of documents, mapping the document to one or more of a plurality of topics. The document is associated with a user. For each user, the user is mapped to each of the plurality of topics that are mapped to documents with which the user is associated. One of the users is matched to a conversation according to the mappings of the users to those of the plurality of topics that are also mapped to the conversation.