This International Standard refines the Basic Reference Model for OSI to provide a framework for co-ordinating the development of existing and future Application Layer standards. It is provided for reference by Application Layer standards.In particular this International Standard:a) defines the nature of standards in the Application Layer and the relationships among them;b) defines the architectural framework in which individual OSI Application Layer protocols shall be developed.c) defines the categories of identifiable objects which are necessary for the specification and operation of protocols;d) relates distributed information processing activities to the standards in the Application Layer.This International Standard does not specify services and protocols for OSI. It is neither an implementation specification for systems, nor a basis for appraising the conformance of implementations. Further, it addresses neither the requirements for, nor the form of, documentation of such services and protocols.