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Lesson 7 - UML - Activity Diagram

In the previous lesson, UML - State Machine Diagram, we introduced the State machine diagram. We learned it maps the states of a certain entity in the system and transitions between these states. In today's UML tutorial, we're going to take a look at the Activity diagram. It uses the same graphical notation as the State machine, so they can be confused with each other sometimes. However, the Activity diagram is used to display the process, not the state. The process is sometime called workflow which includes the individual steps of the work process, the decision-making between them, and eventually other advanced elements. I believe it's unnecessary to say that the Activity diagram belongs to UML behavioral diagrams.


There are 5 elements in the Activity diagram. Let's describe them.


We draw single actions of the process as rounded rectangles with the action name inside.

Action in an UML Activity diagram

Decision node

We draw decisions for transitions between different branches of the process as diamonds. We don't write anything in the diamond, we write different options as guards in square brackets above the


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In this tutorial, we'll explain the Activity diagram's purpose, why is it better than flowcharts, its elements, and a real-world example.

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Article has been written for you by David Capka
The author is a programmer, who likes web technologies and being the lead/chief article writer at He shares his knowledge with the community and is always looking to improve. He believes that anyone can do what they set their mind to.
Unicorn university The author learned IT at the Unicorn University - a prestigious college providing education on IT and economics.
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