1. A method of recommending an authority on a subject, the method comprising: analyzing documents authored by an author for their semantic footprints; determining, using a processor operatively coupled to a memory, a first intersection of the documents' semantic footprints; associating the first semantic footprint intersection with the author; receiving a query from a user; analyzing the query for its semantic footprint; determining a second intersection, the second intersection being between the query's semantic footprint and the first semantic footprint intersection; and providing the user with information about the author based on an extent of the second intersection.