In addition to the logical three-tier model, the OpenEdge distributed environment supports physical n-tier configurations. Although the n-tier model does not capitalize on the use of shared memory, and introduces an additional network connection that you do not have in the logical three-tier model, the deployment flexibility of this model might have significant benefits from an overall enterprise perspective.

The following figure shows how application logic can be distributed to dedicated machines without any local database connections.

For example, you might want to configure the AppServer or WebSpeed on a system that is a dedicated computation engine with no locally attached database. Then you would use the AppServer to configure a data processing engine to access and filter bulk data from a closely connected database. Thus, you might have a physical three-tier configuration consisting of one or both of the following:

With the AppServer, you can build arbitrary complex applications across any number of computing tiers, based on the business problem that you are trying to solve.

The remaining chapters in this manual help you to understand the OpenEdge Application Server and all of the components that OpenEdge supports for application services development and integration services deployment, and how you can design and implement these services as an integral part of your distributed application computing environment.

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