Free Online UML Activity Diagram Software

An activity diagram is centered around activities, with rounded rectangles representing activities. Transition lines usually do not contain content, except when making judgments, where the condition is written on the line.

A state diagram is centered around states, with rounded rectangles representing states. The content written on the transition line corresponds to the activities in the activity diagram.

ProcessOn features a comprehensive library of UML 2.5 activity diagram and state diagram symbols. Drag-and-drop operation is simple and efficient, with intelligent line snapping. It supports one-click alignment and batch spacing adjustment, allowing you to quickly complete the layout even for complex UML activity diagrams.

Starting Point: An activity diagram begins with a starting point, represented by a solid circle.

Activity: Represents a step or task in the system or business process, indicated by a rounded rectangle with the activity name inside.

Decision: Represented by a diamond shape, also known as branching and merging. A decision has one incoming path and two or more outgoing paths.

Synchronization: Represented by a solid narrow rectangle, also known as fork and join, used to describe parallel processes. A fork indicates the start of parallel activities, while a join indicates the end of parallel activities.

Swimlane: Swimlanes group activities or actions by the executing entity, with each group separated by swimlanes. This clearly describes the transfer of activities or actions and clarifies who completes them.

Object Flow: Represented by a rectangular box for an object, with dashed arrows indicating the dependency between activities and objects.

The granularity of all activity nodes should be roughly the same:

“Logging into the system” and “Clicking a button” appearing together is incorrect.

“Entering username and password” -> “Verifying identity” -> “Entering the main interface” is correct.

At the same time, there are two or more concurrent control flows. A fork indicates a control flow splitting into two or more concurrent control flows, while a join indicates synchronization of two or more concurrent control flows.

In an activity diagram, synchronization bars are used to illustrate the forking and joining of these control flows, represented by solid narrow rectangles.

Business Process Modeling: Procurement approval, leave process

System Function Operation Flow Modeling: Login, order placement, report generation

Behavior Modeling of Classes (in conjunction with state diagrams): User registration process, order processing process

Concurrent or Collaborative Behavior Modeling: Multithreaded collaboration, task distribution

ProcessOn's template community includes various activity diagram application scenario templates that you can clone and use to improve your diagramming efficiency.

1. Keep the graphics simple and avoid excessive nesting

2. Clearly identify the executor of each action

3. Use decision and concurrency structures appropriately

4. Can be used in conjunction with other UML diagrams