Explanation

Diagrams with business actors, business use cases, and relationships among them are called use-case diagrams and illustrate relationships in the business use-case model.

See also Work Product Guideline: Use-Case Diagram.

Use

There are no strict rules about what to illustrate in use-case diagrams. Show what you think are interesting relationships in the model. The following diagrams may be of interest:

• Business actors belonging to the same use-case package.
• A business actor and all the business use cases with which it interacts. A diagram of this type can function as a local diagram of the business actor, and is likely to be related to it.
• Business use cases that handle the same information.
• Business use cases used by the same group of actors.
• Business use cases that are often executed in one sequence.
• Business use cases that belong to the same use-case package.
• The most important business use cases. A diagram of this type can function as a summary of the model.

• A specific business use case and its relationships to business actors and other business use cases. A diagram of this type can function as a local diagram of the business use case, and is likely to be related to it.

It is recommended that you include each business actor, business use case, and relationship in at least one of the diagrams. If it makes the business use-case model clearer, they can be part of several diagrams and you can show them several times in the same diagram.