Shallow history (shallowHistory) represents a return to only the topmost substate of the most recent state configuration, which is entered using the default entry rule. Source Unified Modeling Language 2.5.1
When exiting from a composite State, exit commences with the innermost State in the active state configuration. This means that exit Behaviors are executed in sequence starting with the innermost active State. Source Unified Modeling Language 2.5.1
shallowHistory – ... A single outgoing Transition from this Pseudostate may be defined terminating on a substate of the composite State. This substate is the default shallow history state of the composite State. Source Unified Modeling Language 2.5.1
