This paper proposes a framework for protecting privacy and avoiding the unnecessary propagation of identity information while facilitating exchange of specific information needed by Internet systems to personalize and control access to services. It also sets out factors to be taken into consideration when deciding where the standardization of such a framework should be brought about. Information systems that co-operate to originate, control and consume identity information have been called identity systems. The evolution of the Internet requires increased interoperability of these systems. Such interoperability demands an abstract model that encompasses the characteristics of all co-operating identity systems. We call this abstract model the Identity Metasystem.