1. A method for generating a document taxonomy based upon tag data in groupings of tags, the method comprising: retrieving into memory of a host computer different groupings of tags for correspondingly different documents providing a bottom-up view of the documents; deriving a folksonomy from the groupings of tags for the documents; organizing the folksonomy into a hierarchy of nodes, each of the nodes being associated with a different subject in the folksonomy; and, publishing the hierarchy of nodes as a taxonomy for the documents to provide a top-down view of the documents.