Use cases share different kinds of relationships. Structuring Use Case Diagram with Relationships The entire system can span all of these modules depicting the overall system boundary.
can form a system boundary for use cases specific to each of these business functions. For example, for an ERP system for an organization, each of the modules such as personal, payroll, accounting, etc. For large and complex systems, each modules may be the system boundary. The system boundary is potentially the entire system as defined in the requirements document. Actors may be connected to use cases by associations, indicating that the actor and the use case communicate with one another using messages. The participation of an actor in a use case is shown by connecting a actor to a use case by a solid link. Each Actor must be linked to a use case, while some use cases may not be linked to actors. System function (process - automated or manual). Actor has responsibility toward the system (inputs), and Actor have expectations from the system (outputs). Similar to the concept of user, but a user can play different roles. Someone interacts with use case (system function). Notation DescriptionVisual Representation Use Case Diagram at a GlanceĪ standard form of use case diagram is defined in the Unified Modeling Language as shown in the Use Case Diagram example below: As you can see, use case diagrams belong to the family of behavioral diagrams. The figure below shows the UML diagram hierarchy and the positioning of UML Use Case Diagram. If yours contain more than 20 use cases, you are probably mis-using usecase diagram. 
It does not show the order in which steps are performed to achieve the goals of each use case.Īs said, a use case diagram should be simple and contains only a few shapes.It only summarizes some of the relationships between use cases, actors, and systems.It does not show the detail of the use cases: A use case diagram consists of the system, the related use cases and actors and relates these to each other to visualize: what is being described? ( system), who is using the system? ( actors) and what do the actors want to achieve? ( use cases), thus, use cases help ensure that the correct system is developed by capturing the requirements from the user’s point of view.Ī use case diagram is usually simple. A use case describes how a user uses a system to accomplish a particular goal.
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