description: allow for a check digit and a check digit scheme to be conveyed as part of Identifier. The rules of the ID Type determine if the check digit is part of the ID value or sent separately. package_name: hl7.fhir.uv.extensions derivation: constraint name: IDCheckDigit type: Extension elements: extension: {index: 0} url: pattern: {type: Uri, value: 'http://hl7.org/fhir/StructureDefinition/identifier-checkDigit'} index: 1 value: choices: [valueString] index: 3 valueString: {type: string, choiceOf: value, index: 4} package_version: 5.1.0 extensions: {} class: extension kind: complex-type url: http://hl7.org/fhir/StructureDefinition/identifier-checkDigit base: http://hl7.org/fhir/StructureDefinition/Extension version: 5.1.0 required: [valueString, value]