Usecase diagrams are a type of diagram that are used to model the interactions between the actors and the usecases of the system.
An actor is a person or a system that interacts with the system. Actors are represented by a rectangle with the name of the actor written inside it.
A usecase is a task that the system performs. Usecases are represented by an ellipse with the name of the usecase written inside it.
A usecase diagram is a diagram that shows the actors and the usecases of the system. The diagram is represented by a rectangle that contains the name of the system inside it. The actors are represented by rectangles and the usecases are represented by ellipses.
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