The MVC pattern that is embodied by Struts provides an standard way to separate logic, presentation and data in modular applications, among the three application tiers, as shown in Figure 13-1:
The model is the set of data and business rules for the application. This is commonly called the application’s business logic. This business logic in most cases involves access to data stores, legacy systems and external applications.
The view is the application’s user interface. This tier is also known as the presentation layer.
The controller defines the way that an application interacts with user input and the model, that is, the overall flow of events. This is called the application logic.