allowed metadata are only ones detailed on the TF 2a,  3.18.4.1.2.3.7.1

self.slot->forAll(sl : SlotType1 | (not sl.name.oclIsUndefined()) and (sl.name='$XDSDocumentEntryClassCode' or sl.name='$XDSDocumentEntryTypeCode' or 
sl.name='$XDSDocumentEntryPracticeSettingCode' or sl.name='$XDSDocumentEntryCreationTimeFrom' or sl.name='$XDSDocumentEntryCreationTimeTo' or 
sl.name='$XDSDocumentEntryServiceStartTimeFrom' or sl.name='$XDSDocumentEntryServiceStartTimeTo' or sl.name='$XDSDocumentEntryServiceStopTimeFrom' 
or sl.name='$XDSDocumentEntryServiceStopTimeTo' or sl.name='$XDSDocumentEntryHealthcareFacilityTypeCode' or sl.name='$XDSDocumentEntryEventCodeList' or sl.name='$XDSDocumentEntryConfidentialityCode' 
or sl.name='$XDSDocumentEntryAuthorPerson' or sl.name='$XDSDocumentEntryFormatCode' or sl.name='$XDSDocumentEntryPatientId' or sl.name='$XDSDocumentEntryStatus' ) )