Designing a UML 2.0 Activity Diagram

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Use the following tips and techniques when you design a UML 2.0 Activity Diagram. Usually you create Activity Diagrams after State Machine Diagrams.

To design a UML 2.0 Activity Diagram, follow this general procedure:

  1. Create one or more activities. You can place several activities on a single diagram, or create a separate diagram for each.

    Warning: You cannot create nested activities.

  2. Usually activities are linked to states or transitions on State Machine Diagrams. Switch to your State Machine Diagrams and associate the activities you just created with states and transitions.

    Tip: After that you can find that some more activities must be created, or the same activity can be used in several places.

  3. Switch back to the Activity Diagram. Think about flows in your activities. You can have an object flow (for transferring data), a control flow, both or even several flows in each activity.
  4. Create starting and finishing points for every flow. Each flow can have the following starting points:
    • Initial node
    • Activity parameter (for object flow)
    • Accept event action
    • Accept time event actionEach flow finishes with a Activity Final or Flow Final node.If your activity has several starting points, they can be used simultaneously.
  5. Create object nodes. You do not link object nodes to classes on your Class Diagrams. However, you can use hyperlinks for better understanding of your diagrams.
  6. Create action nodes for your flows. Flows can share actions.

    Warning: You cannot create nested actions.

  7. For object flows, add pins to actions. Connect actions and pins by flow links.
  8. Add pre- and postconditions. You can create plain text or OCL conditions.
  9. You can optionally create shortcuts to related elements of other diagrams.

To add an activity parameter to an activity:

  1. In the Tool Palette, press the Activity Parameter button.
  2. Click the target activity.Or:Choose Add > Activity Parameter on the activity context menu.

Result: An Activity Parameter node is added to the activity as a rectangle. Note that the activity parameter node is attached to its activity. You can only move the node along the activity borders.

Note: Activity parameters cannot be connected by control flow links.

See Also