The scope of a transition is the lowest XOR state in the hierarchy of states that is a proper common ancestor of all the sources and targets of a transition, including non-basic states that are explicit sources or targets of transition arrows appearing in the transition. When a transition is taken, all proper descendants of the scope in which the system resides at the beginning of the step are exited, and all proper descendants of that scope in which the system will reside as a result of executing the transition are entered. Thus, the scope is the lowest state in which the system stays, without exiting and re-entering, when taking the transition. Conflicting Transitions Conflicting transitions are those that can lead the system into distinct states. Multiple transitions that can occur at the same time step in a given scope have the same priority.
Priority is given to the transition with the higher scope.
Conflicting states at the same priority must resolve non-determinism to be legal. The system described in a statechart changes state and executes actions based on execution steps. These execution steps determine a sequence of dynamic changes. They are logical intervals, and are not associated with a particular time. At any given step n , the system evaluates the events that were generated and identifies the values of data items and conditions that are present at the occurrence of step n .