A use case diagram
is a visual representation used in software engineering to depict the interactions between system actors
and the system itself
. It captures the dynamic behavior of a system by illustrating its use cases
and the roles that interact with them. These diagrams are essential in specifying the system's functional requirements
and understanding how users will interact with the system. By providing a high-level view, use case diagrams help stakeholders understand the system's functionality and its potential value. PlantUML
offers a unique approach to creating use case diagrams through its text-based language. One of the primary advantages of using PlantUML is its simplicity and efficiency
. Instead of manually drawing shapes and connections, users can define their diagrams using intuitive and concise textual descriptions. This not only speeds up the diagram creation process but also ensures consistency and accuracy
. The ability to integrate with various documentation platforms and its wide range of supported output formats make PlantUML a versatile tool for both developers and non-developers. Lastly, being open-source
, PlantUML boasts a strong community
that continually contributes to its improvement and offers a wealth of resources for users at all levels.
Use cases are enclosed using between parentheses (because two parentheses looks like an oval).
You can also use the
keyword to define a usecase. And you can define an alias, using the
keyword. This alias will be used later, when defining relations.
The name defining an actor is enclosed between colons.
You can also use the
keyword to define an actor. An alias can be assigned using the
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.
You can change the actor style from stick man (by default)
- an awesome man with the
skinparam actorStyle awesome command;
- a hollow man with the
skinparam actorStyle hollow command.
Stick man (by default)
Awesome man [Ref. QA-10493]
Hollow man [Ref. PR#396]
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.
You can use packages to group actors or use cases.
You can use
to change the display of the package.
To link actors and use cases, the arrow
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.
If one actor/use case extends another one, you can use the symbol
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
keywords, then linked to other objects using the
You can add stereotypes while defining actors and use cases using
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
keywords inside the arrow:
You can shorten the arrow by using only the first character of the direction (for example,
) or the two first characters (
Please note that you should not abuse this functionality : Graphviz
gives usually good results without tweaking.
And with the
left to right direction
keywords to split your diagram into several pages or images.
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.
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.
You can add
to make Business Use Case.
Business Actor[Ref. QA-12179]
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]
You can change the color
or style of individual element using the following notation:
[Ref. QA-5340 and adapted from QA-6852]
Simple example[Ref. QA-15481]
For another example, see on JSON page