B2B Integration : A Practical Guide to Collaborative E-commerce

Middleware Technologies 235
Each framework is a book in itself. Some aspects of these frameworks,
such as MOM (MSMQ and JMS), have been previously touched upon
in this chapter due to their ever-increasing importance in distributed
systems. For the purpose of brevity, this section will focus on the
distributed object/component element of each framework.
8.4.3. OMA — CORBA 3
The common object request broker architecture, or CORBA, was the
first successful distributed architecture protocol to be developed. CORBA
is a distributed object/component technology that is platform and
language independent and allows remote object creation and remote
object method invocation.
OMA architecture
CORBA is a protocol based on the object management architecture
(OMA) developed by the OMG. The OMG is a consortium formed in
1989 to define the standards and protocols required for distributed
object systems in heterogeneous environments. OMG's objective is the
definition of the OMA, which includes four sets of standards: the
Common Object Request Broker Architecture (CORBA), Common Object
Services Specification (COSS), Common Facilities and Application
Objects. Unlike the COM and EJB protocols, the CORBA and OMA
protocols are developed by a consortium which helps ensure that the
final specification is product or technology independent.
In 1992, OMG first approved the CORBA protocol that defined the
services to be provided by an Object Request Broker (ORB). The ORB is
at the heart of CORBA and ORB provides a mechanism for transparently
communicating between client requests, target objects and other ORBs.
The ORB simplifies distributed programming by decoupling the
client from the details of the method invocations. This makes client's
requests appear to be local procedure calls, when in fact the ORB is
operating on a remote server (see Figure 8.7). When a client invokes an
operation, the ORB is responsible for finding the object implementation,
transparently activating it if necessary, delivering the request to the
object and returning any response to the caller.