UMLR — Message should extend Namespace

Messages in Interactions should extend Namespace similarly as Transition extends Namespace. Being a Namespace (would be backwards compatible) would make it possible to specify Constraints among Parameter of the Signature merely in the context of the particular Message and in addition to the Constraints already applied on the signature itself. This would enable testers to specify fine-grained interdependencies among Parameter (and for argument generation) in that particular situation. Such a feature on Messages would be actually quite handy for test generation purposes – also, similar to what is currently already possible and being done with Transitions.

Any thoughts on that?