description: This extension represents an US Public Health Alternative Expression package_name: rs/hl7.fhir.us.ph derivation: constraint name: USPublicHealthAlternativeExpressionExtension type: Extension elements: url: pattern: {type: uri, value: 'http://hl7.org/fhir/us/ph-library/StructureDefinition/us-ph-alternative-expression-extension'} type: uri index: 0 valueExpression: {type: Expression, index: 1} package_version: library-1.0.0-ballot class: extension kind: complex-type url: http://hl7.org/fhir/us/ph-library/StructureDefinition/us-ph-alternative-expression-extension base: http://hl7.org/fhir/StructureDefinition/Extension version: 1.0.0-ballot