FHIR Extensions Pack
5.1.0 - 5.1.0 (April 2024) International flag

This page is part of the FHIR Core Extensions Registry (v5.1.0: Release 5.1) based on FHIR (HL7® FHIR® Standard) v5.0.0. This is the current published version in its permanent home (it will always be available at this URL). For a full list of available versions, see the Directory of published versions

Extension: Variable - Detailed Descriptions

Page standards status: Trial-use Maturity Level: 3

Definitions for the variable extension.

Guidance on how to interpret the contents of this table can be found here

0. Extension
Definition

Variable specifying a logic to generate a variable for use in subsequent logic. The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.

ShortVariable for processing
Comments

Ordering of variable extension declarations is significant as variables declared in one repetition of this extension might be used in subsequent extension repetitions

For questionnaires, see additional guidance and examples in the SDC implementation guide.

Control0..*
Invariantsvar-1: Variable expressions must have a name (value.name.exists())
2. Extension.extension
Control0..0
4. Extension.url
Fixed Valuehttp://hl7.org/fhir/StructureDefinition/variable
6. Extension.value[x]
Control1..?
TypeExpression, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, RatioRange, Coding, SampledData, id, positiveInt, Distance, Availability, integer64, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, ExtendedContactDetail, CodeableConcept, ParameterDefinition, dateTime, code, string, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, CodeableReference, Signature, unsignedInt, time
[x] NoteSee Choice of Data Types for further information about how to use [x]

Guidance on how to interpret the contents of this table can be found here

0. Extension
Definition

Variable specifying a logic to generate a variable for use in subsequent logic. The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.


Optional Extension Element - found in all resources.

ShortVariable for processingOptional Extensions Element
Comments

Ordering of variable extension declarations is significant as variables declared in one repetition of this extension might be used in subsequent extension repetitions

For questionnaires, see additional guidance and examples in the SDC implementation guide.

Control0..*
Is Modifierfalse
Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
var-1: Variable expressions must have a name (value.name.exists())
2. Extension.extension
Definition

An Extension


May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

ShortExtensionAdditional content defined by implementations
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Control0..0*
TypeExtension
Is Modifierfalse
Summaryfalse
Alternate Namesextensions, user content
Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
SlicingThis element introduces a set of slices on Extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
  • value @ url
    • 4. Extension.url
    Definition

    Source of the definition for the extension code - a logical name or a URL.

    Shortidentifies the meaning of the extension
    Comments

    The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

    Control1..1
    Typeuri
    Is Modifierfalse
    XML FormatIn the XML format, this property is represented as an attribute.
    Summaryfalse
    Fixed Valuehttp://hl7.org/fhir/StructureDefinition/variable
    6. Extension.value[x]
    Definition

    Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

    ShortValue of extension
    Control10..1
    This element is affected by the following invariants: ext-1
    TypeExpression, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, RatioRange, Coding, SampledData, id, positiveInt, Distance, Availability, integer64, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, ExtendedContactDetail, CodeableConcept, ParameterDefinition, dateTime, code, string, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, CodeableReference, Signature, unsignedInt, time
    [x] NoteSee Choice of Data Types for further information about how to use [x]
    Is Modifierfalse
    Summaryfalse
    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))

    Guidance on how to interpret the contents of this table can be found here

    0. Extension
    Definition

    Variable specifying a logic to generate a variable for use in subsequent logic. The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.

    ShortVariable for processing
    Comments

    Ordering of variable extension declarations is significant as variables declared in one repetition of this extension might be used in subsequent extension repetitions

    For questionnaires, see additional guidance and examples in the SDC implementation guide.

    Control0..*
    Is Modifierfalse
    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
    ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
    var-1: Variable expressions must have a name (value.name.exists())
    2. Extension.id
    Definition

    Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

    ShortUnique id for inter-element referencing
    Control0..1
    This element is affected by the following invariants: ele-1
    Typeid
    Is Modifierfalse
    XML FormatIn the XML format, this property is represented as an attribute.
    Summaryfalse
    4. Extension.extension
    Definition

    An Extension

    ShortExtension
    Control0..0
    TypeExtension
    Is Modifierfalse
    Summaryfalse
    Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
    ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
    SlicingThis element introduces a set of slices on Extension.extension. The slices areUnordered and Open, and can be differentiated using the following discriminators:
    • value @ url
      • 6. Extension.url
      Definition

      Source of the definition for the extension code - a logical name or a URL.

      Shortidentifies the meaning of the extension
      Comments

      The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

      Control1..1
      Typeuri
      Is Modifierfalse
      XML FormatIn the XML format, this property is represented as an attribute.
      Summaryfalse
      Fixed Valuehttp://hl7.org/fhir/StructureDefinition/variable
      8. Extension.value[x]
      Definition

      icon Changed:

      Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

      ShortValue of extension
      Control1..1
      This element is affected by the following invariants: ext-1
      TypeExpression
      [x] NoteSee Choice of Data Types for further information about how to use [x]
      Is Modifierfalse
      Summaryfalse
      Invariantsele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))