UMLR — large overlap between structural features and variables

There is large overlap between structural features and variables. For example, examine the structural features actions and compare them to variable action. Upon study, one will discover that structural features and variables have much more in common. In fact, the following equation seems to hold: StructuralFeature = Variable + Feature That is: a variable denotes a location able to hold an instance. A structural feature is a feature of an object and denotes a location ale to hold an instance. Therefore, I suggest that StructuralFeature be made a subtype of Variable. In the infrastructure, variable would have no interpretation, other than being an abstract metaclass indicating the ability to hold a value. In the superstructure, variable is concrete as described in Activities. Not only would this allow to eliminate the duplication of actions related to accessing variables, but also, other duplications (as, e.g., with respect to their being connectable elements and the related explanations) could be avoided.