The following table describes the elements that you can add to Use Case diagrams. The elements are grouped by Modeling Palette section and are also listed if they appear on the Context Menu.
Element | Icon | Description |
---|---|---|
Basic Section | ||
Use Case | ![]() |
The description of what a system does, not how the system does it. A Use Case contains multiple scenarios, each of which describes a specific flow of events through the Use Case. Scenarios in Use Cases must be described clearly enough for outsiders to understand. |
Package | ![]() |
A grouping of model elements. Packages are used in Use Case, Class, and Component diagrams. A Package can be nested within another Package, and can contain both subordinate packages and ordinary model elements. Packages can be subsystems of models. The entire system description can be thought of as a single, high-level subsystem package containing all of the system's modeling elements. |
Actor | ![]() |
A coherent set of roles that users of a system play when interacting with the system's Use Cases. Actors can be anything: human beings, devices, or other systems. Actors can have attributes and operations, which do not appear on the Actor element, but in the Documentation window. A physical object can play several roles and thus can be modeled by several Actors. |
Comment | ![]() |
A Notepad notation. Use Comments to record information for an element or link in a diagram. This information is not included in generated code but is for information only. Each Comment can contain unlimited text, and can be numbered. You can also define a stereotype, and enter a noted element. |
Context Palette | ||
Include (from Use Case) | ![]() |
The dependency between Use Cases in which the source use case explicitly incorporates the behavior of another Use Case at a specified location. |
Extend (from Use Case) | ![]() |
A dependency between Use Cases in which the Use Case extends the behavior of the source. |
Generalization (from Use Case or Actor) | ![]() |
Generalization is the taxonomic relationship between a more general element and a more specific element that is fully consistent with the first element and that adds additional information. This link is also known as a specialization or inheritance link |
Association (from Use Case or Actor) | ![]() |
The link that associates an Actor to a Use Case. This link shows participation of an Actor in a Use Case and is the only relationship between Actors and Use Cases. |
Link Comment (from Use Case) | ![]() |
The connection between the comment element and the associated element. |
Dependency | ![]() |
The relationship between two elements whose definitions depend on one another in such a way that changes to one can result in changes to the other. For example, when one class mentions another as an operation parameter, or as part of its data, the two classes exhibit dependency. |
Realize | ![]() |
A semantic relationship between classifiers. One classifier specifies a contract that another classifier guarantees to carry out. These relationships are used in two places: between interfaces and the classes that realize them, and between use cases and the collaboration that realize them. |
Usage | ![]() |
A dependency in which one element (the client) requires the presence of another element (the supplier) for its correct functioning or implementation. |
Permission | ![]() |
A dependency that signifies granting of access rights from the supplier model element to a client model element, in which the client requires access to some or all of the constituent elements of the supplier. |
Abstraction | ![]() |
A boundary relative to the perspective of the viewer. The essential characteristics of an entity that distinguish it from all other kinds of entities. |