description: An expression that returns a boolean value for whether to enable the item. If the expression does not resolve to a boolean, it is considered an error in the design of the Questionnaire.  Form renderer behavior is undefined.  Some tools may attempt to force the value to be a boolean (e.g. is it a non-empty collection, non-null, non-zero - if so, then true).  Systems SHOULD present a warning to the user if a non-boolean valued expression result does not trigger an all-out error.
package_name: hl7.fhir.uv.sdc.r4b
derivation: constraint
name: EnableWhenExpressionExtension
type: Extension
elements:
  url:
    type: uri
    pattern: {type: Uri, value: 'http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression'}
    index: 0
  value:
    constraint:
      inv-1: {human: FHIR query language not allowed., source: 'http://hl7.org/fhir/StructureDefinition/Element', severity: error, expression: language!='application/x-fhir-query'}
    choices: [valueExpression]
    index: 2
  valueExpression:
    type: Expression
    constraint:
      inv-1: {human: FHIR query language not allowed., source: 'http://hl7.org/fhir/StructureDefinition/Element', severity: error, expression: language!='application/x-fhir-query'}
    choiceOf: value
    index: 3
package_version: 3.0.0
class: extension
kind: complex-type
url: http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-enableWhenExpression
base: http://hl7.org/fhir/StructureDefinition/Extension
version: 3.0.0