Enterprise application integration technology:

Enterprise application integration technology is based on middleware technology
that has been around for years. The goal is to take advantage of these
technologies so that data in heterogeneous information technology landscapes
can be integrated properly. In addition to data integration, the processes that
the application systems realize also need to be integrated. This means that
one system performs certain steps and then transfers control to another system
which takes the results and continues operation. In the context of this
book, the process integration part of enterprise application integration is at
the centre of attention.
Enterprise application integration faces the problem that each integration
project requires design and implementation efforts that might be considerable.
When directly linking each pair of applications, system integrators run into
the N � N problem, meaning that the number of interfaces to develop rises
to the square of the number N of applications to be integrated.
A sketch of this integration issue is represented in Figure 2.5, where N = 6
of siloed applications and their integration links are shown. Each link represents
an interface that connects the application systems associated with it.
Therefore, the number of interfaces between pairs of application systems
realize grows to the order of N �N, incurring considerable overhead. If there
were links between any pairs of application systems, then the number of interfaces
to develop would be 5 + 4 + 3 + 2 + 1 = 15. In the general case, the
number of links between N application systems is and therefore rises to the square
of the number of application systems. In the
scenario shown, not all pairs of application systems are connected, but the
problem of the large number of interfaces can nevertheless be seen .
In enterprise computing, changes are abundant, and a systems architecture
should support changes in an efficient and effective manner. The enterprise
application integration architecture resulting from point-to-point integration
does not respond well to changes. The reason is due to the hard-wiring of the
interfaces. Any change in the application landscape requires adaptation of the
respective interfaces. This adaptation is typically realized by reprogramming
interfaces, which requires considerable resources.
A specific realization platform of enterprise application integration is
message-oriented middleware, where applications communicate by sending
and receiving messages. While conceptually the middleware realizes a centralized
component, the direct connection between the applications�and therefore
the point-to-point integration�is still in place, because each sender needs
to encode the receiver of a message.
The main aspect of message-oriented middleware is execution guarantees,
such as guaranteed message delivery. However, the problem mentioned above
is not solved, since any change in the application landscape needs to be implemented
by changing the communication structure of applications.