ISO 9506-2:2003

ISO 9506 is an Application Layer communication specification, in accord with the OSI communication model. It provides a set of services appropriate to communications between automated equipment and systems that interrogate or control them. Its description of interactions follow the client server model. It is suitable for use over any network that supports full-duplex, reliable communication, such as the Internet.
Part 1 provides a set of abstract models of information objects that may be found in such automated systems, and the specifications of a set of abstract services that operate on these models.
ISO 9506-2:2003 provides the protocol for the messages to be exchanged between client and server to realize support for the abstract services defined in Part 1.