Structured Data Capture
4.0.0 - STU 4 International flag

This page is part of the Structured Data Capture FHIR IG (v4.0.0: STU 4) based on FHIR (HL7® FHIR® Standard) R4. This is the current published version. For a full list of available versions, see the Directory of published versions

Extension: Candidate Answers Expression

Official URL: http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-candidateExpression Version: 4.0.0
Standards status: Trial-use Active as of 2026-03-24 Maturity Level: 4 Computable Name: CandidateExpressionExtension
Other Identifiers: OID:2.16.840.1.113883.4.642.40.17.42.18

A FHIRPath or CQL expression, or FHIR Query that resolves to a list of candidate answers for the question item or that establishes context for a group item. The user may select from among the candidates to choose answers for the question.

Context of Use

Additional details on the use of this extension can be found on the Form Behavior and Questionnaire Population pages. For further guidance on candidateExpression refer to the Expressions page - candidateExpression section.

Usage info

Usages:

You can also check for usages in the FHIR IG Statistics

Formal Views of Extension Content

Description Differentials, Snapshots, and other representations.

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Extension 0..1 Extension Expression for possible answers
... extension 0..0 Extension
... url 1..1 uri "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-candidateExpression"
... value[x] 0..1 Expression Value of extension

doco Documentation for this format
NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Extension 0..1 Extension Expression for possible answers
... id 0..1 string Unique id for inter-element referencing
... extension 0..0 Extension
Slice: Unordered, Open by value:url
... url 1..1 uri "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-candidateExpression"

doco Documentation for this format

Constraints

Id Grade Path(s) Description Expression
ele-1 error **ALL** elements All FHIR elements must have a @value or children hasValue() or (children().count() > id.count())
ext-1 error **ALL** extensions Must have either extensions or value[x], not both extension.exists() != value.exists()

Summary

Simple Extension with the type Expression: A FHIRPath or CQL expression, or FHIR Query that resolves to a list of candidate answers for the question item or that establishes context for a group item. The user may select from among the candidates to choose answers for the question.

Maturity: 4

Differential ViewDifferential View

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Extension 0..1 Extension Expression for possible answers
... extension 0..0 Extension
... url 1..1 uri "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-candidateExpression"
... value[x] 0..1 Expression Value of extension

doco Documentation for this format

Snapshot View

NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
.. Extension 0..1 Extension Expression for possible answers
... id 0..1 string Unique id for inter-element referencing
... extension 0..0 Extension
Slice: Unordered, Open by value:url
... url 1..1 uri "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-candidateExpression"

doco Documentation for this format

Constraints

Id Grade Path(s) Description Expression
ele-1 error **ALL** elements All FHIR elements must have a @value or children hasValue() or (children().count() > id.count())
ext-1 error **ALL** extensions Must have either extensions or value[x], not both extension.exists() != value.exists()

Summary

Simple Extension with the type Expression: A FHIRPath or CQL expression, or FHIR Query that resolves to a list of candidate answers for the question item or that establishes context for a group item. The user may select from among the candidates to choose answers for the question.

Maturity: 4

 

Other representations of profile: CSV, Excel, Schematron