Currently the elements .referrer and .interpreter only allow for QI Core Practitioner.

Because a Practitioner might be referring or interpreting only in a specific role, we suggest that QI Core PractitionerRole also be allowed for these two fields.  i.e. Dr Jones might be a radiology but also act as an ER doctor.  For interpreter, you would want to specify the PractitionerRole and then Dr Jones.  Also some quality contracts may only cover a practitioner as defined in a specific PractitionerRole.

A .referrer might be just a QI Core Organization so please consider adding that to this field as well.  Not sure this would be appropriate for an interpreter though