<status value="draft" /> <experimental value="false" /> <date value="2026-02-26" /> <publisher value="NHS Wales" /> <contact> <name value="FHIR Standards" /> <telecom> <system value="email" /> <value value="fhir.standards@wales.nhs.uk" /> <use value="work" /> <rank value="1" /> </telecom> </contact> <copyright value="2026 NHS Wales" /> <fhirVersion value="4.0.1" /> <kind value="complex-type" /> <abstract value="false" /> <context> <type value="element" /> <expression value="DocumentReference" /> </context> <type value="Extension" /> <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Extension" /> <derivation value="constraint" /> <differential> <element id="Extension"> <path value="Extension" /> <short value="An explicitly assigned identifer of a variation of the content in the DocumentReference." /> <definition value="This is a business version identifier, not a resource version id. It can be used to store the SetSequenceNumber of a document from the Welsh Care Records Service. (Backport from FHIR R5.)" /> </element> <element id="Extension.extension"> <path value="Extension.extension" /> <max value="0" /> </element> <element id="Extension.url"> <path value="Extension.url" /> <fixedUri value="https://fhir.nhs.wales/StructureDefinition/Extension-DataStandardsWales-DocumentReference.version" /> </element> <element id="Extension.value[x]"> <path value="Extension.value[x]" /> <type> <code value="string" /> </type> </element> </differential> </StructureDefinition>