Resumen
Common Object Request Broker Architecture (CORBA) object model relies to a large degree on semantics of object references. An object reference uniquely identifies a local or remote object instance, clients can only invoke an operation on an object if they hold a reference to it. Apart from the ability to denote remote objects and to convert to and from strings, CORBA references have semantics that are similar to those of C++ class pointers, references can dangle and they can be nil. Object references are opaque. Application code is not allowed to look inside a reference or to make any assumptions about its internals. The details of how an object reference identifies an object and how requests are dispatched to their correct destination are carefully hidden away in ORBS run-time support. Semantics of object references have profound implications on the design of an ORB, in particular its ability to support object migration and to scale to very large number of objects. Some mechanisms and design trade-offs involved are explained in this article, including some speculation on how CORBA should evolve to address needs of ever-larger distributed systems.