Adding expansion regions and expansion nodes to activity diagrams

An expansion region is a structured activity that can run multiple iterations. An expansion node is a type of object node that represents the flow into or out of an expansion region. An expansion node can contain a collection of inputs and outputs of the same type.

Before you begin

You must have UML Element Building Blocks, UML Activity 3 enabled for the model. In the Project Explorer, right-click the model and click Properties. In the Properties view, click Capabilities in the drop menu. In the Capabilities page expand UML Element Building Blocks and enable UML Activity 3.


  1. In the Palette, on the Actions page, click beside Structured Activity and click Expansion Region.
  2. In the diagram editor, click where you want to place the expansion region.
  3. In the Palette, click beside Object node and click Expansion Node.
  4. Click the expansion region to place the Expansion Node within it.
  5. Optional: To specify a mode for the expansion region, click the region, click the Properties view, click the Advanced page, click the Mode value column, and click an expansion region mode.


You can add additional input and output expansion nodes to the expansion regions. You can also change many of the preferences in the Properties view, on the Advanced page.