description: Used when the actual type is not allowed by the definition of the element, or not specified in the context (e.g. in a cross-version extension). In general, this should only arise when wrangling between versions using cross-version extensions - see [Cross Version Extensions](versions.html#extensions). For legacy reasons, this extension has a type of `string` but it behaves as a URI with a default namespace (per ElementDefinition.type.code). Also note that the default namespace behavior is version independent
package_name: hl7.fhir.uv.extensions.r5
derivation: constraint
name: Datatype
type: Extension
elements:
  extension: {index: 0}
  url:
    pattern: {type: uri, value: 'http://hl7.org/fhir/StructureDefinition/_datatype'}
    type: uri
    index: 1
  value:
    choices: [valueString]
    index: 3
  valueString: {type: string, choiceOf: value, index: 4}
package_version: 5.3.0-ballot-tc
extensions: {}
class: extension
kind: complex-type
url: http://hl7.org/fhir/StructureDefinition/_datatype
base: http://hl7.org/fhir/StructureDefinition/Extension
version: 5.3.0-ballot-tc
required: [value, valueString]