OpenEdge distributed application computing models
In contrast, OpenEdge distributed application computing, through the introduction of the AppServer and WebSpeed, expands computing capabilities beyond the limited boundaries of the two-tier model. This section describes the n-tier models described in this chapter in comparison with this two-tier model: the logical three-tier model and the physical n-tier model. As previously mentioned in this chapter, these models help illustrate how you can distribute your application in a OpenEdge distributed environment. You are not limited to using only these models.
Logical three-tier model
The logical three-tier model, as shown in Figure 1–2, has a user interface that is physically separate from another machine that contains the application logic and the data. Physically, all three logical tiers can also be hosted on a single machine. Therefore, physically there are only one or two machines, but technically, or logically, there are three tiers: the user interface, the application logic, and the data.
The configuration of the logical three-tier model promotes the writing of business logic and deploying them on an application server close to the data. An OpenEdge implementation of this model has the AppServer or WebSpeed connect to the database server using shared memory; the need to access the database over the network has been eliminated, providing faster data access to the business logic that processes it.
Another important feature of this model is the fact that the AppServer or WebSpeed remotely processes the information and only returns the results to the user interface. This capability minimizes the number of network messages while it delivers the specific data you need.
Physical n-tier model
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.
Figure 1–3 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:
WebSpeedWith 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.
For more information on the:
- OpenEdge Application Server and the development of application services, including support for integration services, see Chapter 2, " OpenEdge Application Server Architecture."
- Development of integration services in particular, see Chapter 7, " OpenEdge Messaging and ESB."