Provides a conceptual and terminological framework for the other parts of this Standard. The functional and organizational models define ways in which the Directory can be distributed, both functionally and administratively; the security model defines the framework within which security features, such as access control, are provided; and the information model describes the logical structure of the directory information base. This Standard is identical with and has been reproduced from ISO/IEC 9594-2:1990 including Technical Corrigendum 1:1991.