3. Distribution types

If we project the types of software components we have analyzed onto real systems, we can reduce the types of client/server models to three broad categories. Each of these types has its own advantages and disadvantages, which we shall now highlight.

When data access system services are located on a system separate from the system running the application, we speak of a client/data server model. When all or part of the presentation services provided by the system are located on a separate system from the one running the application, we speak of a presentation client/server, and when the application processing functions relating to an interaction are distributed over separate systems, we speak of a processing client/server.

In practice, the distribution of processing can involve two or three physical systems. So far, we've defined the client/server...