@Override
public void setExisting(DmcAttribute<?> attr) {
existingValue = (DmcTypePrimitiveSVREFMV) attr;
if (existingValue != null) value = existingValue.getMVCopy();
}
@Override
public void resetToExisting() {
if (existingValue == null) value = null;
else value = existingValue.getMVCopy();
}