State Transition
Passage from one node to another is represented by a transition.
All authorized transitions must be defined. Those that are not defined are prohibited.
Creating a Transition
To create an transition between two states in a State Machine Diagram:
1. In the state machine diagram, click Transition 
in the insert toolbar.
in the insert toolbar.2. Click the source state and drag the mouse to the target state.
3. Release the mouse button. The association is created.
Transition Types
A transition can be external, internal or local.
You can specify the transition type in the Characteristics property page of the transition.
• An external transition is a transition that modifies the active state.
• An internal transition enables an object to react to the arrival of an event that does not result in a state change but has an effect such as calling an operation or sending a message. For example, when pulling items from inventory, an item may not change state if the quantity remaining in the inventory is sufficient and does not fall below the reorder level or shortage level.
• A local transition applies to sub-states of a composite state. It can cause a change of state only within the composite state.