PSCS11 — RemoveStructuralFeatureValueAction should destroy constructor links

PSCS updates the semantics for ClearStructuralFeatureValueAction, so that, "when a StructuralFeature is cleared, any links representing an instance of a Connector in which the StructuralFeature is involved are destroyed" (see 8.2.2.2.2 CS_ClearStructuralFeatureActionActivation).

However, there is no similar update to the semantics for RemoveStructuralFeatureValueAction. So, if a single value is removed from a StructuralFeature, it is possible that this value will still have links to it that are instances of Connectors from within the composite. This violates the semantics of Connectors, whose instances are only supposed to link values within properties of the containing composite object.

Recommendation: Add a CS_RemoveStructuralFeatureValueActionActivation to destroy relevant connector links to a value when the value is removed from a structural feature.

RemoveStructuralFeatureValueAction should destroy constructor links

As suggested in the issue description, PSCS is required to provide an extension to the semantics defined by fUML for RemoveStructuralFeatureValueAction (see section 8.6.3.2.12 in [fUML 1.2.1]). The defined extension will be in charge, when a value is removed from a feature value, to destroy all links (i.e., instances of connectors) in which the removed value is involved.

In order to capture the new semantics, CS_RemoveStructuralFeatureValueActionActivation visitor is required to be included in the PSCS semantic model. This visitor class must be defined as a specialization of RemoveStructuralFeatureValueActionActivation. It overrides the doAction operation of its superclass. The doAction operation captures the exact same semantics than the one defined in fUML however it add the possibility to propagate the impact of the removed value(s) to the relevant connectors. This propagation is ensured in getLinkToDestroy and propagateDestructionToLinks which respectively find the connectors instances to destroy and perform the actual destruction.

As a side adjustment, CS_ExecutionFactory instantiateVisitor operation is updated to enable the creation of a CS_RemoveStructuralFeatureValueActionActivation.