description: Indicates whether the list of supported units (conveyed in other extensions) are the exhaustive list from which the user must choose or whether they're able to select alternate codes or specify a string. package_name: hl7.fhir.uv.sdc.r4b derivation: constraint name: UnitOpen type: Extension elements: url: type: uri pattern: {type: Uri, value: 'http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-unitOpen'} index: 0 value: choices: [valueCode] index: 2 valueCode: {type: code, choiceOf: value, index: 3} package_version: 3.0.0 class: extension kind: complex-type url: http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-unitOpen base: http://hl7.org/fhir/StructureDefinition/Extension version: 3.0.0 required: [valueCode, value]