Use Cases: Patterns and Blueprints

Chapter 8. Extend: Expanding Existing Use Cases

Extend Relationship

When subsequent iterations in a project are performed or when later versions of a system's use-case model are developed, completely new use cases are often added to the model and new actions are inserted into existing use cases. This means that the existing services are extended with some additional features that did not exist in the previous versions of the model. However, the different stakeholders often do not want to modify the existing use cases because these have already been reviewed and approved. They are only willing to have certain features added to the existing use cases. Therefore, the developers will have to express these additions without modifying the existing use ...