DocumentGroup 

All types of documents, paper or electronic such as itineraries or
trailers or tickets. xxxAdd : This need be expanded to hold document specific data, such
as numbers

Element Group Information

Model

Document | Documents
Children: Document, Documents

Used By

Complex Types AccomodationType, AgencyType, AgentType, AirportType, AmountAdjustmentType, AmountTaxType, AuthorType, BookingType, BrandType, CabinType, CancellationType, CarrierType, CityType, ClientType, CompanyType, ContinentType, CountryType, CountyType, CustomerType, DeliveryMethodElectronicType, DeliveryMethodMailType, DeliveryMethodPickupType, DeliveryMethodType, DistanceType, DistributorType, DocumentBoardingPassType, DocumentCancellationRulesType, DocumentCertificateType, DocumentCollectionType, DocumentConfirmationType, DocumentContractType, DocumentDriverLicenceType, DocumentFollowUpType, DocumentIdentityCardType, DocumentInsuranceType, DocumentInvoiceStatementType, DocumentInvoiceType, DocumentNoticeType, DocumentPassportType, DocumentPaymentStatementType, DocumentQuotationType, DocumentReceiptType, DocumentResidentPermitType, DocumentSellingConditionsRulesType, DocumentTicketType, DocumentTravelDocumentType, DocumentType, DocumentVisaType, DocumentVoucherType, DomainType, GuaranteeMethodType, GuaranteeType, HotelType, LocationFloorType, LocationSellLocationType, LocationShopType, LocationSwimmingPoolType, LocationType, PaymentType, PersonType, PriceFareType, PriceInvoiceType, PriceQuotationType, PriceStoredFareType, PriceType, RegionType, RequesterType, RestaurantType, RoomBedroomType, RoomKitchenType, RoomMeetingRoomType, RoomStorageType, RoomType, RuleQuantityType, RuleType, SegmentActivityType, SegmentAirType, SegmentCombinedType, SegmentDocType, SegmentDocVisaType, SegmentEventType, SegmentExcursionType, SegmentFeeType, SegmentFoodType, SegmentInsuranceType, SegmentMiscellaneousType, SegmentParkingType, SegmentProductType, SegmentRailType, SegmentRoadType, SegmentServiceType, SegmentStageType, SegmentStayType, SegmentSurfaceType, SegmentTourType, SegmentTransferType, SegmentTransportationType, SegmentType, SegmentVehicleType, SegmentWaterType, ShipDeckType, ShipType, SlopeType, StaffType, StationType, StationVehicleDropOffType, StationVehiclePickupType, StationVehicleType, StopType, StyleType, TicketType, TransactionDataRequestType, TransactionDataResponseType, TransactionDataType, TransactionRequestType, TransactionResponseType, TransactionTravelType, TransportationMeanType, TravellerType, TripType, VehicleMakerType, VendorProviderType, VendorRetailerType, VendorType, VendorWholesaler
Elements County, IdentityCard, Passport, State, Terminal, Visa

Source 

<xs:group name="DocumentGroup">
  <xs:annotation>
    <xs:documentation>All types of documents, paper or electronic such as itineraries or trailers or tickets. xxxAdd : This need be expanded to hold document specific data, such as numbers</xs:documentation>
  </xs:annotation>
  <xs:choice>
    <xs:annotation>
      <xs:documentation>One or many</xs:documentation>
    </xs:annotation>
    <xs:element ref="Document"/>
    <xs:element ref="Documents"/>
  </xs:choice>
</xs:group>