UML 2.0 in a Nutshell

Advanced Use Case Modeling

As it does for other classifiers, UML provides mechanisms for reusing and adding on to use cases and actors. You can expand an actor's capabilities or replace entire use cases using generalization . You can factor out common elements of use cases using included use cases, or add on to base use cases using use case extension.

Actor and Use Case Generalization

Though not officially mentioned in the specification, actors and use cases can be generalized like many other classifiers. Actor generalization is typically used to pull out common requirements from several different actors to simplify modeling. For example, Figure 7-10 shows several administrators and the use cases they need to invoke. You may have a Database Administrator, a Backup Administrator, and a Deployment Administrator, all with slightly different needs. However, the majority of the needs of the individual actors may overlap. You can factor out a generic System Administrator actor to capture the common functionality, and then specialize to identify the unique needs of each actor.

You represent actor generalization like any other classifier; draw a solid line, with a closed arrow pointing from the specialized actor to the base actor. Figure 7-11 shows the same information as Figure 7-10 but in a much easier-to-read diagram.

Use cases may be generalized as well. Typically use case generalization is used to express some high-level functional need of a system without going into specifics. Specializations ...