description: Identifies the id of the source message used to construct the actual error message. package_name: hl7.fhir.uv.extensions derivation: constraint name: OOIssueMessageId type: Extension elements: extension: {index: 0} url: pattern: {type: Uri, value: 'http://hl7.org/fhir/StructureDefinition/operationoutcome-message-id'} 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/operationoutcome-message-id base: http://hl7.org/fhir/StructureDefinition/Extension version: 5.1.0 required: [valueString, value]