Tiers and Data
Tiered systems built with Visual Basic are essentially systems of class instances provided by a number of physical components. The components can be deployed on a number of machines interacting to produce system behavior. This means the class instances share their data with the system through class interface methods, properties, and events. Figure 12-5 illustrates how data and objects fit together at the simplest level.
Figure 12-5 Objects and their data.
A class is a template of functionality-it is a generic functional wrapper around data variables. It comes to life when you createan instance of it and give it some specific data to hold in its variables. It is possible to have data-only classes composed only of properties. It is equally possible to have functionality-only classes composed entirely of methods. In both cases a developer's first reaction to such classes should be to question their design. However, such classes are the exception rather than the rule.