UML14 — Use of interfaces in associations

The issue / problem relates to the use of interfaces in associations, i.e.
the "type" association in the meta model between AssociationEnd and
Classifier.

Besides the use of a syntactical interface specification, I use the
interfaces as well as the location to provide semantics, using OCL.

OCL provides a well-defined way to navigate along association ends. Where
actually interfaces would provide the semantic context for association ends,
I have to refrain from specifiying those on the interface, but have to defer
this association to the realizing class.

As an alternative it is possible to provide getter and setter operations
providing access to the association ends in the deferred implementation. But
this presents two other problems:
a) this public (as no other ones are allowed) operation on the interface
will need to be realized any realizing class (and I do not always want to
compromise this information)
b) the return value of the operation (in case of a multiplicity > 1) will
not per se have the same OCL "accessibility" as an association end;
furthermore tools - at this point in time - provide significant better
control in terms of verification for associations than for operation
parameters / return values.

rejected