The concept of a use case is pretty broad. There are many different things called use cases that are written up in many different ways. That's fine - it's the concept of having a detailed description of a business process that is important.
The format that we used earlier in this chapter is a simple prose or text description of the process. A couple of other popular formats that we might encounter include: a step-by-step outline in a table format, a flowchart or a flow diagram.
Functional use cases are typically grouped together with the higher-level requirements use case from which they flowed. All of these use cases, when combined, provide a solid and traceable base of documentation for the subsequent design, development, testing and documentation of the system.
Functional use cases frequently include user-interface mock-ups, often created in Visual Basic to look somewhat like the screen that the users will see at the end. This can be very useful, because it can help the users visualize the flow of the system as they proof our use case descriptions.
Developing prototype screens using Visual Basic can be very powerful. Not only can we create screens to assist our users in visualizing the system, but, if we're careful, we can get a significant head start on the development of the UI itself. Visual Basic is not only good for prototyping - it's also good for easily converting prototypes into full-blown applications without having to start over from scratch.