UML - Activity Diagram Symbols' Meaning
Activity diagrams are as simple to make as an ordinary flowchart. Each symbol has a meaning and context where its use is appropriate. Check out our guide for a detailed list of UML activity diagram symbols meaning.
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Activity Diagram Symbols' Meaning
The start symbol represents the beginning of a process or workflow in an activity diagram. It can be used by itself or with a note symbol that explains the starting point.
The activity symbol is the main component of an activity diagram. These shapes indicate the activities that make up a modeled process.
The connector symbol is represented by arrowed lines that show the directional flow, or control flow, of the activity. An incoming arrow starts a step of an activity; once the step is completed, the flow continues with the outgoing arrow.
The join symbol, or synchronization bar, is a thick vertical or horizontal line. It combines two concurrent activities and re-introduces them to a flow where only one activity occurs at a time.
A fork is symbolized with multiple arrowed lines from a join. It splits a single activity flow into two concurrent activities.
The decision symbol is a diamond shape; it represents the branching or merging of various flows with the symbol acting as a frame or container.
The note symbol allows the diagram creators or collaborators to communicate additional messages that don't fit within the diagram itself.
The receive signal symbol demonstrates the acceptance of an event. After the event is received, the flow that comes from this action is completed.
The send signal symbol means that a signal is being sent to a receiving activity, as seen above.
The shallow history pseudostate symbol represents a transition that invokes the last active state.
The option loop symbol allows the creator to model a repetitive sequence within the option loop symbol.
The flow final symbol shows the ending point of a process' flow. While a flow final symbol marks the end of a process in a single flow, an end symbol represents the completion of all flows in an activity.
The end symbol represents the completion of a process or workflow.
Using Symbols in an Activity Diagram
In Lucidchart, creating an activity diagram from scratch is surprisingly simple. Just open up the correct shape library, drag out symbols from the toolbox to the canvas, then model the process flow by drawing lines between shapes. It's easy to resize and style any element. You can even import SVG shapes and Visio files for a custom solution. If you'd like to learn more about UML, check out our guide to Activity Diagrams or our What is UML tutorial.
Lucidchart offers standard UML 2.0 shapes, so you can easily make and share activity diagrams. Whether it's for school or work, your UML diagrams will be professional and easy to read. Try it for yourself!