Examples are specified at: "Examples.Synchronization".
A common use case when modeling orthogonal regions is to allow two regions to change their state only in an atomic way. This means either both transitions are allowed to fire or both transition are not allowed to fire. Sending and receiving synchronizations via synchronization channels synchronize the firing of transitions of parallel regions. A synchronization channel has to be specified at a common ancestor state of the parallel regions and serves as the type for the synchronizations using it.
Sending a synchronization via the synchronization channel from one sender transition
to a receiver transition performs a synchronization. We allow only a receiving synchronization or sending synchronization per transition.
A synchronization affects the prioritization and execution order of parallel transitions as described in the following. The sender transition is executed before the receiver transition because a synchronization is directed from sender to receiver. This may violate region priorities when the sender transition is in a region with a lower priority than the region of the receiver transition because without the sending and the receiving of synchronizations between them the transition in the region with the higher priority would be executed first.