State Transitions
Passage from one node to another is represented by a transition.
A transition is passage of an object from one state to another. A transition is the response of an object to an event it receives. When an event occurs and certain conditions are satisfied, the object executes certain actions while still in the first state, before passing to the second state.All authorized transitions must be defined. Those that are not defined are prohibited.
Examples of transitions:
For the marital status of a person, certain transitions are possible:
• It can change from the "unmarried" to the "married" state
• It can change from the "married" to the "divorced" state.
Other transitions are not possible:
• The state cannot change from "unmarried" to "divorced".
Creating a Transition
To create an transition between two states:
1. In the state machine diagram, click Transition (UML) 
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.
External transition
An external transition is a transition that modifies the active state.
Internal transition
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.
Local transition
A local transition applies to sub-states of a composite state. It can cause a change of state only within the composite state.
Transition Effects
Triggering of a transition can be accompanied by an effect. The effect can be represented by:
• An activity
• A collaboration
• An interaction
• A state machine
To define effect of a transition:
1. Open the Characteristics property page of the transition.
2. Click the arrow in the Effect (Behavior) box and create or connect the object that defines the effect.
Transition Effect Display
To modify how the transition effects are displayed.
1. In the state machine diagram, right-click the transition and select Shapes and Details.
2. Then select “Effect” in the tree that appears.
You can now specify whether to display all or part of the transition effects and their characteristics.
Transition Triggering Event
In the properties dialog box of a transition in the Event tab, you can indicate the Event Kind that triggers a transition.
It can be:
• Any event
• Calling an operation
• Changing the object concerned by the transition
• Creating an object
• Destruction of an object
• Sending a signal
• Sending an operation
• Sending a signal from the object
• Receiving a signal
• Receiving an operation
• A timer
A timer is an event determined only by time elapsed. Example: Monday, at 4 pm, etc.Fields displayed under Event Kind vary according to the event kind selected.
You can select the object concerned by the effect.
In the case of an operation or signal, you can specify values of parameters sent.