FHIR Extensions Pack
5.3.0-ballot-tc1 - (September 2025 Ballot) International flag

FHIR Extensions Pack, published by HL7 International / FHIR Infrastructure. This guide is not an authorized publication; it is the continuous build for version 5.3.0-ballot-tc1 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/fhir-extensions/ and changes regularly. See the Directory of published versions

Extension: ValueSet Expression

Official URL: http://hl7.org/fhir/StructureDefinition/valueset-expression Version: 5.3.0-ballot-tc1
Standards status: Trial-use Maturity Level: 3 Responsible: HL7 International / Terminology Infrastructure Computable Name: VSExpression
Other Identifiers: OID:2.16.840.1.113883.4.642.5.1211

An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to make the same statement as the expression. If there is no compose, the expression is the only definition of the value set and the ValueSet definition (compose) can only be evaluated by a system that understands the syntax used in the expression.

Context of Use

This extension may be used on the following element(s)

Usage info

Usages:

You can also check for usages in the FHIR IG Statistics

Changes since version 5.2.0:

  • No changes

    • Formal Views of Extension Content

    Description of Profiles, Differentials, Snapshots, and how the XML and JSON presentations work.

    This structure is derived from Extension

    Summary

    Simple Extension with the type Expression: An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to make the same statement as the expression. If there is no compose, the expression is the only definition of the value set and the ValueSet definition (compose) can only be evaluated by a system that understands the syntax used in the expression.

    Maturity: 3

    This structure is derived from Extension

    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..1 Extension An alternative computable expression of the value set content
    ... extension 0..0 Extension
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/valueset-expression"
    ... value[x] 1..1 Expression Value of extension

    doco Documentation for this format
    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..1 Extension An alternative computable expression of the value set content
    ... id 0..1 id Unique id for inter-element referencing
    ... extension 0..0 Extension
    Slice: Unordered, Open by value:url
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/valueset-expression"

    doco Documentation for this format

    This structure is derived from Extension

    Summary

    Simple Extension with the type Expression: An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to make the same statement as the expression. If there is no compose, the expression is the only definition of the value set and the ValueSet definition (compose) can only be evaluated by a system that understands the syntax used in the expression.

    Maturity: 3

    Differential View

    This structure is derived from Extension

    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..1 Extension An alternative computable expression of the value set content
    ... extension 0..0 Extension
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/valueset-expression"
    ... value[x] 1..1 Expression Value of extension

    doco Documentation for this format

    Snapshot View

    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..1 Extension An alternative computable expression of the value set content
    ... id 0..1 id Unique id for inter-element referencing
    ... extension 0..0 Extension
    Slice: Unordered, Open by value:url
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/valueset-expression"

    doco Documentation for this format

     

    Other representations of profile: CSV, Excel, Schematron

    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()

    R4B

    The extension is unchanged in R4B

    R4

    The extension is unchanged in R4

    R3

    The extension is represented a little differently in R3:

    • Replace the type Expression with a set of extensions for the content of the type along with the _datatype extension
    • Note: Extensions that have been modified for R3 are still draft while real-world experience is collected
    Name Flags Card. Type Description & Constraints      Filter: Filters doco
    . . Extension 0..1 Extension An alternative computable expression of the value set content
    . . . Slices for extension 0 ..* Extension Extension
    Slice: Unordered, Open by value:url
    . . . . extension:_datatype 1..1 (Complex) DataType name 'Expression' from R5
    URL: http://hl7.org/fhir/StructureDefinition/_datatype
    . . . . . value[x] 1.. 1 string Value of extension
    Fixed Value: Expression
    . . . . extension:description 0..1 Extension Natural language description of the condition
    . . . . . extension 0 .. 0 Extension
    . . . . . url 1 .. 1 uri "description"
    . . . . . value[x] 1.. 1 string Value of extension
    . . . . extension:name 0..1 Extension Short name assigned to expression for reuse
    . . . . . extension 0 .. 0 Extension
    . . . . . url 1 .. 1 uri "name"
    . . . . . value[x] 1.. 1 code Value of extension
    . . . . extension:language 0..1 Extension text/cql | text/fhirpath | application/x-fhir-query | etc.
    . . . . . extension 0 .. 0 Extension
    . . . . . url 1 .. 1 uri "language"
    . . . . . value[x] 1.. 1 code Value of extension
    Binding: ExpressionLanguage ( extensible ) : The media type of the expression language.
    Additional Bindings Purpose
    MimeTypes Max Binding
    . . . . extension:expression 0..1 Extension Expression in specified language
    . . . . . extension 0 .. 0 Extension
    . . . . . url 1 .. 1 uri "expression"
    . . . . . value[x] 1.. 1 string Value of extension
    . . . . extension:reference 0..1 Extension Where the expression is found
    . . . . . extension 0 .. 0 Extension
    . . . . . url 1 .. 1 uri "reference"
    . . . . . value[x] 1.. 1 uri Value of extension
    . . . url 1 .. 1 uri "http://hl7.org/fhir/StructureDefinition/valueset-expression"
    . . . value[x] 0 .. 0 Value of extension

    doco Documentation for this format

    Search Parameters for this Extension

    (none found)