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The GIOP specification consists of the following elements:
• The Common Data Representation (CDR) definition. CDR is a transfer syntax mapping OMG IDL data types into a bicanonical low-level representation for “onthe-wire? transfer between ORBs and Inter-ORB bridges (agents).
• GIOP Message Formats. GIOP messages are exchanged between agents to facilitate object requests, locate object implementations, and manage communication channels.
• Internet IOP Message Transport. The IIOP specification describes how agents open TCP/IP connections and use them to transfer GIOP messages.
• GIOP Transport Assumptions. The GIOP specification describes general assumptions made concerning any network transport layer that may be used to transfer GIOP messages. The specification also describes how connections may be managed, and constraints on GIOP message ordering.
The IIOP specification adds the following element to the GIOP specification:
The IIOP is not a separate specification; it is a specialization, or mapping, of the GIOP to a specific transport (TCP/IP).
The GIOP specification (without the transport-specific IIOP element) may be considered as a separate conformance point for
future mappings to other transport layers.
The complete OMG IDL specifications for the GIOP and IIOP are shown in
Section 15.10, “OMG IDL,? on page 15-60. Fragments of the specification are used
throughout this chapter as necessary.