KERML — Specify default direction for the ownedParameterMember of a ParameterMembership

The validateParameterMembershipParameterHasDirection constraint requires that the ownedMemberParameter of a ParameterMembership have a non-null direction – which is what makes it a parameter. However, it does not specify what the direction should be.

Now, for a ReturnParameterMembership, the validateReturnParameterMembershipParameterHasDirectionOut requires that the direction be out. The validateParameterMembershipParameterHasDirection should be updated so that, for a non-return parameter, the default direction is in.

Revise the validateParameterMembershipParameterHasDirection constraint

A better approach than suggested in the issue is to define an operation parameterDirection() on ParameterMembership and then revise the constraint so that it requires the direction of the ownedParameterMember to be equal to the result of parameterDirection(). The operation can then be specified to return in for ParameterMembership, but redefined to return out for ReturnParameterMembership. No additional constraint is then required to enforce this on ReturnParameterMembership.