Database Reference
In-Depth Information
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Message-Oriented Middleware (MOM)
: Is based on the notion of developing distributed
applications that integrate at the message level but across the network.
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Distributed Object Technology (DOT)
: Is based on the notion of developing distributed appli-
cations that integrate at the interface level but those that make the application look like an
object.
◾
Transaction Processing Monitors (TPMs)
: Is based on the notion of developing distributed
applications that integrate at the distributed transaction level but across the network.
10.2.2 Models of Integration
An integration model defines the approach and configurations used to integrate software applica-
tions depending on the nature and methods of the envisaged integration. There are three possible
points of integration, namely, presentation, functional, and data integration.
10.2.2.1 Presentation Integration
In this model, the integration is accomplished by deploying a new and uniform application user
interface: the new application appears to be a single application although it may be accessing
several legacy and other applications at the back end. The integration logic, the instructions on
where to direct the user interactions, communicates the interaction of the user to the correspond-
ing 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.
10.2.2.2 Functional Integration
In this model, the integration is accomplished by invoking from other applications functionality or
business logic of the existing applications by using code-level interfaces to the existing applications.
This might be achieved at the level of an object or a procedure or via application 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,
for changing the customer's address in an enterprise application, the functionality 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 middleware 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 categories of distributed process-
ing are as follows:
