<status value="draft" /> <fhirVersion value="4.0.1" /> <kind value="complex-type" /> <abstract value="false" /> <type value="Identifier" /> <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Identifier" /> <derivation value="constraint" /> <differential> <element id="Identifier.system"> <path value="Identifier.system" /> <min value="1" /> <mustSupport value="true" /> </element> </differential> </StructureDefinition>