3. The method according to claim 2 , wherein the diverse data sources are distributed among a set of autonomous organizations comprising at least first and second organizations, and wherein assigning the classification comprises classifying the user according to an organizational affiliation of the user so as to control access by users in the first organization to the data sources held by the second organization.
2. The method according to claim 1 , wherein defining the ontology comprises specifying a user ontology, and wherein defining the data access rights comprises assigning a classification to a user according to the user ontology, and also comprising comparing the classification to the access rights applicable to the data.