UML24 — Activity vs Action completion

"In both UML activities and UML statecharts it is sometimes necessary to recognize when some behavior (activity or state-based, respectively) has completed. However, in models without an explicit final node or final state respectively, it is not always clear when this condition is achieved

This is covered for Activities in the UML 2.5 beta specification this is now covered in Subclause 15.2.3 under “Activity
Execution”:
“The execution of an Activity with no streaming Parameters completes when it has no nodes executing and no nodes
enabled for execution, or when it is explicitly terminated using an ActivityFinalNode (see sub clause 15.3). The
execution of an Activity with streaming input Parameters shall not terminate until the cumulative number of values
posted to each of those input Parameters (by the invoker of the Activity) is at least equal to the Parametermultiplicity
lower bound. The execution of an Activity with streaming output Parameters shall not terminate until the cumulative
number of values posted to each of those output Parameters (by the Activity itself) is at least equal to the Parameter
multiplicity lower bound.”
A StateMachine that does not reach a final state simply does not terminate (unless it is terminated by an explicit
external action, such as the destruction of its context object).
Disposition: Closed - No Change