FAQ 35.09 What are the important concepts behind CORBA?

The key concepts are

1. Platform and language independence

2. Location transparency

3. An OO approach that includes interface inheritance within IDL

4. Interoperability between ORBs

5. A consensus-based industry standards process

CORBA uses the proxy design pattern to achieve platform and language independence. A proxy is a stand-in, or surrogate, for a "real" object and provides a client-side reference for accessing a server object that could be located anywhere. By decoupling the software architecture from the runtime environment, the software becomes more flexible and decisions such as which objects reside where can be controlled by a network administrator armed with time sensitive information that was not available to the software architects when they were designing the system.

IDL is a language for defining the interfaces for distributed objects, where the interfaces are similar to C++ abstract base classes with only pure virtual member functions. The IDL compiler converts the interface specification into the target language, which can be C, C++, Java, and so on. CORBA IDL supports interface inheritance, but since it is not an implementation programming language, it does not support inheritance of implementation (however implementation inheritance is normally used when implementing an IDL interface in an OO programming language such as C++).

ORBs from different vendors can communicate seamlessly because of the Internet Inter-ORB Protocol (IIOP), which runs over TCP/IP. The specification also supports DCE as the communications layer, but most CORBA users choose TCP/IP.