The Common Object Request Broker Architecture (CORBA) is an open, vendor-independent specification for distributed computing. It is published by the Object Management Group (OMG).
Most applications need different objects on various platforms and operating systems to communicate with each other across networks. CORBA enables objects to interoperate in this way, using the Internet Inter-ORB Protocol (IIOP). To help objects understand the operations available, and the syntax required to invoke them, an Interface Definition Language (IDL) is used. The IDL is programming-language independent, to increase the interoperability between objects.
When an application developer defines an object, they also define other aspects. The aspects include the position of the object in an overall hierarchy, object attributes, and possible operations. Next, the aspects are all described in the IDL. The description is then converted into an implementation by using an IDL compiler. For example, IDLJ is an IDL compiler for the Java™ language, and converts an IDL description into a Java source code. The benefit of this is that the object implementation is encapsulated by the IDL definition. Any other objects wanting to interoperate can do so using mechanisms defined using the shared IDL.
Developers enable this interoperability by defining the hierarchy, attributes, and operations of objects using IDL. They then use an IDL compiler (such as IDLJ for Java) to map the definition onto an implementation in a programming language. The implementation of an object is encapsulated. Clients of the object can see only its external IDL interface. The OMG has produced specifications for mappings from IDL to many common programming languages, including C, C++, and Java
An essential part of the CORBA specification is the Object Request Broker (ORB). The ORB routes requests from a client object to a remote object. The ORB then returns any responses to the required destinations. Java contains an implementation of the ORB that communicates by using IIOP.