# Use Case Diagram

## Create Use Case Diagram

To create a Use Case Diagram:

1. Select first an element where a new Use Case Diagram to be contained as a child.
2. Select **Model | Add Diagram | Use Case Diagram** in Menu Bar or select **Add Diagram | Use Case Diagram** in Context Menu.

> **See also**
>
> [UML Use Case Diagram](http://www.uml-diagrams.org/use-case-diagrams.html) - For more information about UML Use Case Diagram.

## Use Case Subject

To create an Use Case Subject:

1. Select **Use Case Subject** in **Toolbox**.
2. Drag on the diagram as the size of Use Case Subject.

You can use **QuickEdit** for Model Element (See [Model Element](https://docs.staruml.io/v3/class-diagram#model-element)).

## Actor

To create an Actor:

1. Select **Actor** in **Toolbox**.
2. Drag on the diagram as the size of Actor.

To create an Actor (model element only) by Menu:

1. Select an Element where a new Actor to be contained.
2. Select **Model | Add | Actor** in Menu Bar or **Add | Actor** in Context Menu.

You can use **QuickEdit** for Actor by double-click or press `Enter` on a selected Actor.

* **Name Expression** : Edit name expression.

  *Syntax of Name Expression*

  ```
  expression ::= [ '<<' stereotype `>>` ] [ visibility ] name
  stereotype ::= (identifier)
  visibility ::= '+' | '#' | '-' | '~'
  name ::= (identifier)
  ```
* **Visibility** : Change visibility property.
* **Add Note** : Add a linked note.
* **Add Attribute** (`Ctrl+Enter`) : Add an attribute.
* **Add Operation** (`Ctrl+Shift+Enter`) : Add an operation.
* **Add Sub-Actor** : Add a sub-actor.
* **Add Super-Actor** : Add a super actor.
* **Add Associated Use Case** : Add an associated use case.

To suppress Attributes, see [Suppress Attributes](https://docs.staruml.io/v3/user-guide/formatting-diagram#suppress-attributes).

To suppress Operations, see [Suppress Operations](https://docs.staruml.io/v3/user-guide/formatting-diagram#suppress-operations).

To show or hide Operation Signatures, see [Show Operation Signature](https://docs.staruml.io/v3/user-guide/formatting-diagram#show-operation-signature).

## Use Case

To create an Use Case:

1. Select **Use Case** in **Toolbox**.
2. Drag on the diagram as the size of Use Case.

To create an Use Case (model element only) by Menu:

1. Select an Element where a new Use Case to be contained.
2. Select **Model | Add | Use Case** in Menu Bar or **Add | Use Case** in Context Menu.

You can use **QuickEdit** for Use Case by double-click or press `Enter` on a selected Use Case.

* **Name Expression** : Edit name expression.

  *Syntax of Name Expression*

  ```
  expression ::= [ '<<' stereotype `>>` ] [ visibility ] name
  stereotype ::= (identifier)
  visibility ::= '+' | '#' | '-' | '~'
  name ::= (identifier)
  ```
* **Visibility** : Change visibility property.
* **Add Note** : Add a linked note.
* **Add Extension Point** (`Ctrl+Enter`) : Add an extension point.
* **Add Associated Actor** : Add an associated actor.
* **Add Included Use Case** : Add an included use case.
* **Add Extended Use Case** : Add an extended use case.

To suppress Attributes, see [Suppress Attributes](https://docs.staruml.io/v3/user-guide/formatting-diagram#suppress-attributes).

To suppress Operations, see [Suppress Operations](https://docs.staruml.io/v3/user-guide/formatting-diagram#suppress-operations).

To show or hide Operation Signatures, see [Show Operation Signature](https://docs.staruml.io/v3/user-guide/formatting-diagram#show-operation-signature).

## Extension Point

To add an Extension Point:

1. Select an Use Case.
2. Select **Model | Add | Extension Point** in Menu Bar or **Add | Extension Point** in Context Menu.

You can use **QuickEdit** for Extension Point by double-click or press `Enter` on a selected Extension Point.

* **Name Expression** : Edit name expression.

  *Syntax of Name Expression*

  ```
  expression ::= [ '<<' stereotype `>>` ] [ visibility ] name
  stereotype ::= (identifier)
  visibility ::= '+' | '#' | '-' | '~'
  name ::= (identifier)
  ```
* **Visibility** : Change visibility property.
* **Add** (`Ctrl+Enter`) : Add one more extension point in the below.
* **Delete** (`Ctrl+Delete`) : Delete the extension point
* **Move Up** (`Ctrl+Up`) : Move the extension point up.
* **Move Down** (`Ctrl+Down`) : Move the extension point down.

## Include

To create an Include:

1. Select **Include** in **Toolbox**.
2. Drag from a Use Case and drop on another Use Case (to be included).

You can use **QuickEdit** for Relationship (See [Relationship](https://docs.staruml.io/v3/class-diagram#relationship)).

## Extend

To create an Extend:

1. Select **Extend** in **Toolbox**.
2. Drag from a Use Case (to be extended) and drop on another Use Case.

You can use **QuickEdit** for Relationship (See [Relationship](https://docs.staruml.io/v3/class-diagram#relationship)).


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