http://hl7.org/fhir/StructureDefinition/elementdefinition-namespace|5.2.0

Use this extension to indicate tha the element has an XML namespace different to http://hl7.org/fhir.

element_id	types
Extension
Extension.extension
Extension.url
Extension.value[x]	uri
Extension
Extension.id	http://hl7.org/fhirpath/System.String
Extension.extension	Extension
Extension.url	http://hl7.org/fhirpath/System.String
Extension.value[x]	uri