CORBA (COMMON OBJECT REQUEST BROKER ARCHITECTURE)

CORBA stands for the Common Object Request Broker Architecture. It is a set of standard mechanisms for naming, locating, and defining objects in a distributed computing environment .It give permission to  programs which are at different locations and developed by different vendors to communicate in a network through an "interface broker." CORBA was developed by a consortium of vendors through the Object Management Group (OMG). CORBA is useful because it provide facility to different  separate pieces of software which are written in different languages and running on different systems to work with each other like a single application or set of services.  The important concept in CORBA is the Object Request Broker (ORB). ORB support in a network of clients and servers on different computers means that a client program  can request services from a server program or object without having knowledge of where is  the server is in a distributed network .To make a requests or to give  replies between the ORBs, programs use the General Inter-ORB Protocol (GIOP) and, for the Internet, its Internet Inter-ORB Protocol (IIOP). The CORBA Interface Definition Language, or IDL, gives permission for the  development of language and location-independent interfaces to distributed objects. Using CORBA, application components can communicate with each other without knowing where they  are located, or who has designed them. CORBA gives the location transparency to be able to execute these applications.

BENEFITS OF CORBA
1.Language independence:-CORBA supports many existing languages. CORBA also supports mixing these languages within a single distributed application. Currently there are many languages supported by various CORBA providers, the most popular are Java and C++.
2.Freedom from technologies:-CORBA provides the facility  to make a level of  the field and allow  teams to develop systems and unit tests that can later be joined together into a whole system. T CORBA allows system elements to be normalized into a single cohesive system model.
3.Operating System independence:-CORBA's design is mean to make operating system independent .CORBA is support Java (OS-independent), as well as natively for Linux/Unix, Windows, Sun, Mac and others.
4.CORBA support strong data type:-CORBA provides flexible data typing, for example an "ANY" data type. CORBA also enforces tightly coupled data typing, reducing human errors. In a situation where Name-Value pairs are passed around, it is conceivable that a server provides a number where a string was expected. CORBA Interface Definition Language provides the mechanism to ensure that user-code conforms to method-names, return-, parameter-types, and exceptions.

USES OF CORBA
CORBA is useful in different  situations. As  of the easy way the CORBA integrates machines from number of many vendors, with sizes ranging from mainframes through minis and desktops to hand-held and embedded systems, it is the middleware of choice for large (and even not-so-large) enterprises. One of the most important, and frequent, uses is in servers those  handle large number of clients, at high hit rates, with high reliability. CORBA is mean to  works behind the scenes in the large  rooms of computers for  the world's largest websites which we are use in everyday life.  CORBA is not used just for large applications different versions of  CORBA used for different purpose like  run real-time systems, and small embedded systems. Thousands of sites rely on CORBA for enterprise, internet, and other computing.

CORBA COMPONENT MODEL (CCM)
The interaction between client and server is mediated by object request brokers (ORBs) on both the client and server sides, communicating typically via IIOP (Internet Inter-ORB Protocol). CORBA objects can be either collocated with the client or distributed on a remote server, without affecting their implementation or use. The details are taken care of by the ORBs.The capabilities of CORBA objects (operations or methods) are defined using the Interface Definition Language (IDL). Operations defined on the interface accept input parameters and return values (both corresponding to some CORBA data-types) and can raise exceptions. The implementation languages supported by CORBA include C, C++, Java, Ada95, COBOL as well as some scripting languages such as Perl, Python, Javascript. Furthermore, CORBA is designed to be independent of the OS and runs on many OS platforms, including Win32, UNIX and real-time embedded systems. Moreover, the communication protocols used by CORBA for ORB communication include TCP/IP, IPX/SPX, ATM, etc.

Life cycle of CORBA application is as follows:

1.Define the service as interfaces in IDL.
2. Compile the IDL to generate client stub and server skeletons,
3. Implement the service and associate it with the skeletons via the portable object adapter (POA) .
4. Publish the service with a Naming or Trading Service for use by clients.
 

And client processing involve

1.contact the Naming Service for the desired service and retrieve the appropriate object reference,
2.invoke operations on the object reference using the IDL-compiler generated stubs. Alternatively, clients can infer the operations supported by the service by consulting an interface repository (IR) and dynamically create requests populating them with the appropriate parameters using the dynamic invocation interface (DII),
3.process incoming reply or exceptions.
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