Building Distributed
Applications
Using the Progress AppServer


The N-tier Model

The n-tier model is a computing model that supports flexible network structuring so that you can distribute application logic and the processing load among many machines across your distributed network. Because the n-tier model can support an unlimited number of clients, partitioning and deploying your application in this manner allows you to break up monolithic applications and flexibly reconfigure them to run in a network environment that better supports your computing needs.

The n-tier model supports the logical separation of user interface, application logic, and data access across three or more machines. Because of this flexibility, application partitioning is closely tied to two basic deployment approaches in a distributed environment: the logical three-tier model and the physical n-tier model.

The logical three-tier model supports separating the application logic from the user interface in the application implementation, and moving it to a remote server where the application data resides. A configuration based on the logical three-tier model remains a physical client/server application in that it is deployed across two machines, but the user interface, application logic, and data are logically separated from one another. In contrast, the physical n-tier model supports both logically and physically discrete segments. Each segment-user interface, application logic, and data-can be deployed on separate machines across the enterprise.

In a Progress distributed environment, you are not restricted to using just these models, and these models can co-exist in a distributed environment. These models are presented in this chapter as a means to understanding the various capabilities available in the Progress distributed environment.


Copyright © 2004 Progress Software Corporation
www.progress.com
Voice: (781) 280-4000
Fax: (781) 280-4095