Convenient ways of specifying sets of data elements, implicitly by
attributes (categories) or explicitly by sets of names
(classes).
- Categories are primarily for
configuring the protection of data. Classes are
primarily for transferring groups of related data elements.
- Categories are likely to be the naming system
that users see and understand. Classes are
primarily of interest to the people running servers.
- Both categories and classes are extensible by both the client
and the server (new data elements can be created within existing
classes, new classes can be created, new categories can be
created, existing data elements can belong to new categories,
etc.)
