A UML use case diagram summarizes how users (or actors) interact with a system, such as a software application. An actor can be a person, an organization, or another system. Use case diagrams show the expected behavior of the system.
Following are the shapes on the UML Use Case stencil.
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Shape |
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Represents a user or external entity that interacts with a system. |
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A coherent unit of functionality provided by a system or class. |
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A system component that may contain multiple use cases. |
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Represents the participation of an actor in a use case. |
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Indicates that one use case has a dependency on another. |
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Indicates that a use case is a specific way to achieve goals of the general use case. |
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Shows how a use case is broken into smaller steps. |
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Shows that one use case adds functionality to another. |
Following are some shapes on the UML Use Case stencil.
Shape | Description |
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Communicates |
In a use case diagram, the communicates relationship defines how an actor participates in a use case. You can add an arrow to the relationship to indicate the direction the information flows. |
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Extends |
In a use case diagram, the extends relationship between two use cases indicates that an instance of use case B, subject to conditions specified in the extension, can include the behavior specified by use case A. The arrowhead in the Extends relationship shape points toward the base use case, not toward the extension. |
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Uses |
In a use case diagram, the uses relationship between two use cases indicates that an instance of use case A will also include behavior as specified by use case B. The arrowhead in the Uses relationship shape points toward the use case being used. |
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Use Case |
In a use case diagram, a use case represents a set of events that occurs when an actor uses a system to complete a process. Normally, a use case is a relatively large process, not an individual step or transaction. |
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Actor |
In a use case diagram, an actor represents a role played by an outside object. One physical object, therefore, can be represented by several actors. A communicates relationship indicates how an actor participates in a use case. |
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System Boundary |
In a use case diagram, the system boundary is a boundary surrounding the use cases which indicate the system. |
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Package |
A package is the basic organizing element of a UML model. Each element belongs to only one package, and one package can be nested in another. You can create new packages or add elements or views (diagrams) to packages by right-clicking icons in the tree view. |
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Interface |
An interface specifies the externally visible operations of a class, component, package, or other element without specifying internal structure. |
