http://hl7.org/fhir/StructureDefinition/valueset-system|4.0.1

Allows a direct reference to the code system for FHIR query.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/canonical
Extension.value[x].targetProfilehttp://hl7.org/fhir/StructureDefinition/CodeSystem