UML22 — completion transitions

Suppose that we have two composite states, nested within to two concurrent regions, which both become "complete" as part of the same "run-to-completion" step, and each of the composite states is the source for a completion transition. I.e. within this "run-to-completion" step two completion events are generated. How should these two completion events be dispatched? - Sequentially, in the same sequential order in which they have been generated. - Sequentially, but any ordering is allowed, - Concurrently. I.e. both completion transitions are considered enabled. - other ??? or any of the above Notice that completion transition may have guards, and activity, hence the firing of one of them may cause the other to become no more "enabled". Hence the above three cases may really cause different system behaviors.

Add a clarification for this case based on the above discussion