description: An expression that determines an initial value for the element on which it appears. The expression may be simply the name of a expression in a referenced library, or it may be a complete inline expression. package_name: hl7.fhir.uv.extensions derivation: constraint name: InitialValue type: Extension elements: extension: {index: 0} url: pattern: {type: uri, value: 'http://hl7.org/fhir/StructureDefinition/cqf-initialValue'} type: uri index: 1 value: choices: [valueExpression] index: 3 valueExpression: {type: Expression, choiceOf: value, index: 4} package_version: 5.3.0-ballot-tc extensions: {} class: extension kind: complex-type url: http://hl7.org/fhir/StructureDefinition/cqf-initialValue base: http://hl7.org/fhir/StructureDefinition/Extension version: 5.3.0-ballot-tc required: [value, valueExpression]