13.1.26.3 Benefits

Prior to supporting valuetypes (objects passable by value), all CORBA objects had object references. When multiple clients invoked on a particular object, they use the same object reference. The instance(s) of the object remained on the server ORB and its state was maintained by the server ORB, not the client ORB.

Valuetypes represent a significant addition to the CORBA architecture. As with objects passed by reference, valuetypes have state and methods, but do not have object references and are always invoked locally as programming language objects. Upon request from the receiving side, valuetypes package their state in the sending context, send their state “over the wire” to the receiving side, where an instance is created and populated with the transmitted state. The sending side has no further control of the client-side instance. Thus, the receiving side can make subsequent invocations of the instance locally. This model eliminates the delays involved when communicating over the network. These delays can be significant in large networks. The addition of valuetypes enables CORBA implementations to more easily scale to meet large data-handling requirements.

Therefore, an essential property of valuetypes is that their implementations are always local. That is, the explicit use of valuetypes in a concrete programming language is always guaranteed to use a local implementation, and will not require a remote call. They have no identity (their value is their identity) and they are not “registered” with the ORB.