What Is Corba ?

           

CORBA, the Common Object Request Broker Architecture defined by the Object Management Group (OMG), specifies how software objects distributed over a network can work together without regard to client and server operating systems and programming languages.

CORBA is a complete distributed object platform. It extends applications across networks, languages, component boundaries, and operating systems. A CORBA Object Request Broker (ORB) connects a client application with the objects it wishes to use.

The client application does not need to know whether the object resides on the same computer or on a remote computer elsewhere on the network. The client application needs to know only two pieces of information: the object's name and how to use the object's interface. The ORB takes care of the details of locating the object, routing the request, and returning the result.

CORBA grew at the same time as three influential trends, which lent credence to the CORBA vision. First, the software development community realized the importance of object-oriented programming techniques, even though they’d been around for the better part of two decades. Second, industry leaders - including IBM, Microsoft, and Apple - were advocating new application models based on small, task-specific components instead of large, general-purpose monoliths. The components would be easy to write and update, since they were small.

Developers could more conveniently, and cheaply, upgrade only those parts of their software that were out of date, and users wouldn't have to purchase entirely new versions of the entire package. And the small components could be distributed over a network more easily than their gargantuan ancestors. The more enlightened of these component architectures promised a cross-platform future, where all components could work together entirely independent of the underlying operating system.

Introduction of CORBA Technology

The Common Object Request Broker Architecture (CORBA) is an emerging open distributed object computing infrastructure being standardized by the Object Management Group (OMG). CORBA automates many common network programming tasks such as object registration, location, and activation; request demultiplexing; framing and error-handling; parameter marshalling and demarshalling; and operation dispatching.

How CORBA Works?

A CORBA Object Request Broker (ORB) is the middleware that establishes the client-server relationship between objects. Using an ORB, a client object can invoke a method on a server object that can be on the same machine or across a network. The ORB intercepts the call and finds an object that can implement the request, pass it the parameters, invoke its method, and return the results. CORBA, like SQL, provides both static and dynamic interfaces to its services. The client does not have to know the object's location, its programming language, its operating system, or any other system aspects that are not part of an object's interface.

The objects are small software components that provide some kind of a service, such as access to a database, account management, or inventory tracking. Fundamental to the architecture are the ORBs. For any client or server to be a part of the CORBA scheme, it must include an ORB to help it find and communicate with other CORBA objects. Once outfitted with an ORB, a client or server can use the services of any CORBA object on any server or host on the network.

An object can be both a client and a server: when it provides services to another object, it's a server; when it requests services from another object, it's a client. The CORBA architecture provides a set of services that help objects interact with each other.

Interface Definition Language

CORBA  defines a special language - IDL -which provides a language-neutral way of describing a specification for a CORBA object and the service(s) it provides. IDL lets components written in different languages communicate with each other using IIOP and the rest of the CORBA architecture.

Currently, it’s easiest to provide an IDL specification for objects written in C, C++, and Java, because the OMG has completed mapping schemes - or translation guides - from IDL to those languages. Also, there are already compilers that employ those mapping schemes to translate IDL to C, C++, and Java. (OMG is currently working on IDL mappings for ADA, SmallTalk, and other languages.)

CORBA objects may sit on different types of systems - Windows or Unix servers, IBM 3090 or DEC VAX mainframes. They may even be written in different languages. In fact, the objects don't need any inherent knowledge of each others' existence. As long as the interface to the service provided by the object is written in IDL, all the objects can communicate and use each others' services through ORBs sitting on clients, servers, database systems, mainframes, and other systems on the network.

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