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envisaged integration. There are three possible points of integration, namely,
presentation, functional, and data integration.
4.2.2.1 Presentation Integration
In this model, the integration is accomplished by deploying a new and uni-
form application user interface—the new application appears to be a single
application although it may be accessing several legacy and other applica-
tions at the back-end. The integration logic, the instructions on where to
direct the user interactions, communicates the interaction of the user to the
corresponding application using their existing presentations as a point of
integration. It then integrates back any results generated from the various
constituent applications. Thus, a single presentation could replace a set of
terminal-based interfaces and might incorporate additional features, func-
tions, and workflow for the user. For instance, a mainframe application
can be integrated into a new Microsoft Windows application at the front-
end using the screen-scraping technology that effectively copies, maps,
and imports data from specific locations on character-based screens of the
mainframe application onto the new schemas and data structures of the
new system.
Presentation integration is the easiest to achieve and can be automated
almost 100%; however, it is also the most limiting of the three models.
4.2.2.2 Functional Integration
In this model, the integration is accomplished by invoking from other
applications functionality or from the business logic of the existing appli-
cations by using code level interfaces to the existing applications. This
might be achieved at the level of an object or a procedure or via applica-
tion programming interface (API) if it exists for each of the corresponding
applications. The business logic includes the processes and workflow as
well as the data manipulation and rules of interpretation. For instance, to
change the customer's address in an enterprise application, the functional-
ity of the existing customer order and billing application can be accessed
if it is functionally integrated with these later applications. Rather than
re-create the logic in the new application, it is more efficient and less error
prone to reuse the existing logic.
Traditionally, remote procedure calls (RPCs), which have been employed
for this kind of integration, have provided the definitions for access and basic
communications facilities. However, lately, distributed processing middle-
ware has become the preferred method of integration as it not only provides
a more robust approach to the interface definitions and communications but
also enables runtime support for intercomponent requests. The three catego-
ries of distributed processing are as follows:
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