Lesson 8

In this module, we walked through the low-level functioning of CORBA clients and servers and checked the major vendors to be sure that their products are compliant with the CORBA specification. As it turned out, they all were, but as we will see in later Modules, this universal support does not continue to be the rule.

CORBA is an open standard rather than a proprietary technology. This is important for a variety of reasons.

1. First, users can choose an implementation from a variety of CORBA vendors or choose one of the freeware implementations.
2. You might think that switching from one CORBA product to another would involve a lot of work.
3. The amount of work involved is likely to be much less than you might think, particularly if you follow the practical advice about how to increase the portability of CORBA-based applications.

In contrast, if you use a proprietary middleware system then switching to another proprietary middleware vendor is much more challenging. The competition between different CORBA vendors helps to keep software prices down.

Finally, many proprietary middleware technologies are designed with the assumption that developers will build all their applications using that particular middleware technology, and so they provide only limited support for integration with other technologies. In contrast, CORBA was designed with the goal of making it easy to integrate with other technologies. Indeed, the CORBA specification explicitly tackles integrations with TMN, SOAP, Microsoft's (D)COM and DCE (a middleware standard that was popular before CORBA). Furthermore, many parts of J2EE borrow heavily from concepts in CORBA, which makes it relatively easy to integrate J2EE and CORBA. Some vendors sell gateways between CORBA and J2EE that make such integration even easier. Several CORBA vendors sell COM-to-CORBA and/or .NET-to-CORBA gateways. This provides a very pragmatic solution to organizations that wish to write GUI applications in, say, Visual Basic on Windows that act as clients to server applications on a different type of computer, such as UNIX or a mainframe. The Visual Basic GUI can be written as a COM/.NET client that thinks it is talking to a COM/.NET server, but in fact communicates with a gateway that forwards on requests to a CORBA server.

CORBA implementations are available for a wide variety of computers, including IBM OS/390 and Fujitsu GlobalServer mainframes, numerous variants of UNIX (including Linux), Windows, AS/400, Open VMS, Apple’s OS X and several embedded operating systems. There are very few other middleware technologies that are available on such a wide range of computers.

Before we move on, take this short quiz about the material we have just covered.
Corba Architecture - Quiz