Chapter 21. Refining the Use Cases

Key Points

• To support development and testing activities, the use cases defined earlier in the project must be more fully elaborated.

• The use-case model is reviewed and will often be refactored as well.

• A well-elaborated use case also defines all alternative flows, pre- and post-conditions, and special requirements.

• The additional use-case relationships extend and include help the team structure and maintain the use-case model.

In the earlier team skills, we introduced use cases as a means of expressing requirements for a system. In this chapter, we'll build on what you learned earlier and show you how to describe your increasingly-detailed understanding of the necessary system behavior. If you've kept your thinking at the right level of specificity so far, the defined use cases are insufficiently detailed to drive design and implementation. Also, it's unlikely that you've defined all of the use cases that would be needed, and you probably haven't considered the exception conditions, state conditions, and other special conditions that are of less interest to the user but that may materially affect the design of the system. The time to add this level of specificity is now.