A Use Case is a UML modeling element that describes how a user of the proposed system interacts with the system to perform a discrete unit of work. It describes and signifies a single interaction over time that has meaning for the end user (person, machine or other system), and is required to leave the system in a complete state: the interaction either completed or rolled back to the initial state. A Use Case:
- Typically has requirements and constraints that describe the essential features and rules under which it operates
- Can have an associated Sequence diagram illustrating behavior over time; who does what to whom, and when
- Typically has scenarios associated with it that describe the workflow over time that produces the end result; alternative workflows (for example, to capture exceptions) are also enabled
Example Use Case diagram
If extending a Use Case, you can specify the points of extension with Use Case Extension Points. To display the attributes, operations or constraints of a Use Case on a diagram, use Rectangle Notation.
Enterprise Architect also provides two stereotyped Use Cases: the Test Case and the Business Use Case.
- Sequence Diagram
- Use Case Extension Points
- Rectangle Notation
- Test Case
- Business Modeling/Interaction
OMG UML Specification:
The OMG Unified Modeling Language specification, (v2.5.1, p.649) states:
A UseCase specifies a set of actions performed by its subjects, which yields an observable result that is of value for one or more Actors or other stakeholders of each subject.