Much as you would design the user interface of any application, you should design each part from which you construct your visual application around a single purpose. For example, consider an application that maintains the customer, order, product, inventory, and employee information of a business--an application common to almost any business. After you clearly identify the roles of the employees and the tasks they perform, it makes sense that you give your application a visual part (window) for each significant task.

For example, consider the order-taker who enters orders into a database, or the director of marketing who analyzes customer and order information looking for demographic trends, or the production manager who analyzes order and inventory information to determine production levels. Each of these specific business tasks should be the single purpose around which your visual part is designed.

Your visual parts can then be combined into a single business-wide application that uses a single logon point to determine which employee is using the application and, therefore, which tasks are available. Each employee has direct access to the visual parts needed to complete the day's tasks, without the interference of any parts of the application that are another employee's responsibility.