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PlantUML Language specification Use Case Diagram
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Use case diagram

A use case diagram shows how external actors interact with a system: who does what, and which features the system exposes. It's a high-level view of functional requirements, useful early in design to align stakeholders.

In PlantUML, you describe actors and use cases in text, and the connections between them. The diagram is generated for you.

See common commands for features available across all diagram types.

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Usecases

Use cases are enclosed using between parentheses (because two parentheses looks like an oval).

You can also use the usecase keyword to define a usecase. And you can define an alias, using the as keyword. This alias will be used later, when defining relations.

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Actors

The name defining an actor is enclosed between colons.

You can also use the actor keyword to define an actor. An alias can be assigned using the as keyword and can be used later instead of the actor's name, e. g. when defining relations.

You can see from the following examples, that the actor definitions are optional.

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Change Actor style

You can change the actor style from stick man (by default) to:

Stick man (by default)

Awesome man

[Ref. QA-10493]

Hollow man

[Ref. PR#396]

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Usecases description

If you want to have a description spanning several lines, you can use quotes.

You can also use the following separators:

By using them pairwise and enclosing text between them, you can created separators with titles.

Please note that the alias and the description are switched around from the basic example:

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Use package

You can use packages to group actors or use cases.

You can use rectangle to change the display of the package.

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Basic example

To link actors and use cases, the arrow --> is used.

The more dashes - in the arrow, the longer the arrow. You can add a label on the arrow, by adding a : character in the arrow definition.

In this example, you see that User has not been defined before, and is used as an actor.

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Extension

If one actor/use case extends another one, you can use the symbol <|--.

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Using notes

You can use the note left of , note right of , note top of , note bottom of keywords to define notes related to a single object.

A note can be also define alone with the note keywords, then linked to other objects using the .. symbol.

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Stereotypes

You can add stereotypes while defining actors and use cases using << and >>.

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Changing arrows direction

By default, links between classes have two dashes -- and are vertically oriented. It is possible to use horizontal link by putting a single dash (or dot) like this:

You can also change directions by reversing the link:

It is also possible to change arrow direction by adding left, right, up or down keywords inside the arrow:

You can shorten the arrow by using only the first character of the direction (for example, -d- instead of -down-) or the two first characters (-do-).

Please note that you should not abuse this functionality : Graphviz gives usually good results without tweaking.

And with the left to right direction parameter:

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Splitting diagrams

The newpage keywords to split your diagram into several pages or images.

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Left to right direction

The general default behavior when building diagram is top to bottom.
You may change to left to right using the left to right direction command. The result is often better with this direction.

See also 'Change diagram orientation' on Deployment diagram page.

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Skinparam

You can use the skinparam command to change colors and fonts for the drawing.

You can use this command :

You can define specific color and fonts for stereotyped actors and usecases.

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Complete example

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Business Use Case

You can add / to make Business Use Case.

Business Usecase

Business Actor

[Ref. QA-12179]

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Change arrow color and style (inline style)

You can change the color or style of individual arrows using the inline following notation:

[Ref. QA-3770 and QA-3816] [See similar feature on deployment-diagram or class diagram]

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Change element color and style (inline style)

You can change the color or style of individual element using the following notation:

[Ref. QA-5340 and adapted from QA-6852]

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Display JSON Data on Usecase diagram

Simple example

[Ref. QA-15481]

For another example, see on JSON page.