FUML11 — LoopNodeActivation does not properly handle termination due to an activity final node

Specification: Semantics of a Foundational Subset for Executable UML Models (fUML) (formal/2011-02-01)

Subclause: 8.5.3.2.3 LoopNodeActivation

If an activity final node directly owned by a loop node fires, then the loop node should terminate. However, the loop node should still produce values on its output pins based on any computations that have happened so far. Currently, when such an activity final node fires, the enclosing loop node is indeed immediately terminated via a call to its terminate(), but this does not actually terminate the loop in LoopNodeActivation::doStructuredActivity(). That loop only terminates once the test part of the loop executes, producing a null value (since all its nodes will no longer be running), which is interpreted as false. Further, the prior call to terminate() removes all tokens from the output pins in the body part of the loop, meaning that they are no longer available to be moved to the output pins of the loop node. As a result, the loop node produces no output, even if outputs have been computed prior to the firing of the final node.

Agreed. Note that the modification of ActivityFinalNodeActivation in the revised text below to use a terminateAll operation from StructuredActivityNodeActivation allows this new operation to be overridden in LoopNodeActivation to specify “last wishes before termination” functionality.