Database Reference
In-Depth Information
Browsers
Client tier
HTTP
Web
servers
Web tier
RMI
.NET remoting IIOP
EJBs
.NET
components
Business component tier
JDBC
SQL
Databases
ERPs
Enterprise information system tier
Figure 10.1
n-tier architecture.
One of the important objectives of application integration is to achieve the integra-
tion between applications with as reduced level of coupling or interdependency as
possible, so that the impact of changes in one application does not affect the other
application(s).
10.2.1 Basic Concepts
The basic concepts related with EAI are described below. A robust and flexible EAI provides a
combination of the methods of integration and modes of communication that are embodied
into the various models of integration that are deployed within the EAI architecture as discussed
later.
10.2.1.1 Methods of Integration
Methods of integration are the approaches used to guide a request from a sender to a receiver. The
two primary methods of integration are described:
1.
Messaging
: In this approach, the sender constructs a message that contains the information
on the actions desired as well as the data required to perform these actions: the message con-
tains both the control information and data. Messages provide a lot of flexibility because the
control information can be easily changed and extended; they are independent of any of the
applications. However, to function correctly, the integration messages must be predefined
precisely so that the messages can be coded and decoded exactly the same way by all senders
and receivers.
2.
Interface
: In this approach, the sender communicates through an interface, which defines
explicitly the actions that can be invoked by an application: the interface is self-describing in
terms of the actions that can be taken. Interfaces make the application look like a procedure
or a method or an object. Interfaces are difficult to change and extend; they are associated
with a particular application.
