A central authority may establish (1), a set of particular structures, classes, restrictions or constraints in SAIF or (2), a set of subtypes of types based on the SAIF data model, SAIF schema, or other schemas. Each set is considered a profile, a saifProfile in the former case and a userProfile in the latter case. (A userProfile may also be defined privately, independent of a central authority. The reader should refer to the comments contained in UserProfile and Tag.) Note that the authority, idName for the profile, and version (or release number) must be specified. This information should be supplied for both saifProfiles and userProfiles.