The region shape is one of the 4 principal shapes used to compose a state diagram.

The region shape is the grouping container for state shapes.

Every state machine diagram must contain a top level region shape which is the container for all states of the state machine.

Region shapes can further be embedded into state shapes which makes the state a composite state. This is accomplished by first converting the state shape to a composite state shape and then adding the region shape as a grouped object to the state shape. A detailed description about this procedure can be found in Create a Composite State.

Figure 1: Root region with two states, composite state containing one and composite state containing two sub-regions

The region shape has a property to define its sequential order in the generated code (execution order) and a property to enable the shallow history function.

The value of the execution order property is shown in a rectangle in the lower left corner of the region.

A circle in the lower left corner containing an "H" indicates that the region has a history. If needed, this history marker can be moved to a different place by dragging its yellow diamond.

Figure 2: Sub-region with history

The initial state of the region, needed for the StateMachineTemplateRegion(String, Boolean) method, is defined through a transition segment shape of type Initial State which is connected to a state within the region.