UML14 — UML 2 Super / Interactions / incorrect multiplicity for PartDecomposition

The description of Lifeline on p. 427 (and Figure 331 on p. 409) indicates that the Lifeline::decomposedAs property is mandatory. This property refers, indirectly through a PartDecomposition, to an interaction the describes the internal workings of the ConnectableElement that the Lifeline represents.

Unfortunately, there are common situations in which the decomposedAs property cannot be specified because the ConnectableElement is not decomposable (i.e., is not structured). In fact, the first constraint on p. 431 in the description of the PartDecomposition metaclass makes this very clear: "PartDecompositions apply only to Parts that are Parts of Internal Structures not to Parts of Collaborations."

Therefore, we would request that the specification be amended to make the Lifeline::decomposedAs property optional (multiplicity [0..1]). If you can amend the generated multiplicity in your API in advance of any changes to the spec, that would be greatly appreciated!

see above