Question

In a state machine diagram with composite states, what is the meaning of a transition that goes from the boundary of a state? What is the meaning of a transition that goes to the boundary of a state?

Answer 1

we will discuss about the transition that goes from and to the boundary of a state but first we have to understand about some facts of transtion in state machine diagram ,

Transition lines depict the movement from one state to another. Each transition line is labeled with the event that causes the transition.

• Viewing a system as a set of states and transitions between states is very useful for describing complex behaviors
• Understanding state transitions is part of system analysis and design
• A Transition is the movement from one state to another state
• Transitions between states occur as follows:
  1. An element is in a source state
  2. An event occurs
  3. An action is performed
  4. The element enters a target state
• Multiple transitions occur either when different events result in a state terminating or when there are guard conditions on the transitions
• A transition without an event and action is known as automatic transitions

In other words ,

Transitions from one state to the next are denoted by lines with arrowheads. A transition may have a trigger, a guard and an effect, as below

source state -------Trigger[guard] / effect -----------> Target state

Source State: The state affected by the transition; if an object is in the source state, an outgoing transition may fire when the object receives the trigger event of the transition and if the guard condition, if any, is satisfied.

Target State: The state that is active after the completion of the transition.

"Trigger" is the cause of the transition, which could be a signal, an event, a change in some condition, or the passage of time. "Guard" is a condition which must be true in order for the trigger to cause the transition. "Effect" is an action which will be invoked directly on the object that owns the state machine as a result of the transition.

now , transition that goes from the boundary of a state, In a state machine diagram with composite states means

- Immediate and effective on any of the substates

and transition that goes to the boundary of a state means

- start the subflow at the initial state of the composite state
- If the composite state is concurrent, then the transition is to each of the
initial states