DDIInstance is the top-level publication wrapper for any DDI document. All DDI content published as XML (with the exception of a Fragment intended for transmission) has DDIInstance as its top level structure. In addition to a citation and coverage statement for the instance, the DDIInstance can contain a Group, ResourcePackage, LocalHoldingPackage or StudyUnit. Additional OtherMaterial content may be added but in general OtherMaterial should be listed in the maintainable object containing the objects the OtherMaterial is related to. The instance can provide an applicable DDIProfile either in-line or by reference and can contain overall translation information.