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

This page is part of the FHIR Core Extensions Registry (v5.3.0-ballot-tc1: Release 5.3) based on FHIR (HL7® FHIR® Standard) v5.0.0. This version is a pre-release. The current official version is 5.2.0. For a full list of available versions, see the Directory of published versions

Extension: Preferred Terminology Server

Official URL: http://hl7.org/fhir/StructureDefinition/preferredTerminologyServer Version: 5.3.0-ballot-tc1
Standards status: Trial-use Maturity Level: 4 Computable Name: PreferredTerminologyServer

Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the resource or a particular portion of the resource (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against (one of) the preferredTerminologyServer(s) rather than the local repository. Systems SHOULD evaluate value sets using terminology servers as follows: First, try any terminology servers declared on the element in question. If there are more then one, try them in the order they appear. Then try any servers that appear on ancestor elements in order of closest ancestor up to any on the resource root If there are no declared servers or none of the ones listed provide a useful response, the form filler may then try any of the typical servers it would normally use. A 'useful response' means a response that provides a valid (though potentially empty) expansion. Clients MAY wish to log/report errors returned by terminology servers.

Not all terminology servers will necessarily have access to the codes. If a questionnaire points to value sets, the rendering engine needs to know where to get a current expansion.

Context of Use

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

Usage info

Usages:

  • This Extension is not used by any profiles in this Implementation Guide

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 url: Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the resource or a particular portion of the resource (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against (one of) the preferredTerminologyServer(s) rather than the local repository. Systems SHOULD evaluate value sets using terminology servers as follows: First, try any terminology servers declared on the element in question. If there are more then one, try them in the order they appear. Then try any servers that appear on ancestor elements in order of closest ancestor up to any on the resource root If there are no declared servers or none of the ones listed provide a useful response, the form filler may then try any of the typical servers it would normally use. A 'useful response' means a response that provides a valid (though potentially empty) expansion. Clients MAY wish to log/report errors returned by terminology servers.

    Maturity: 4

    This structure is derived from Extension

    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..* Extension Preferred terminology server
    ... extension 0..0
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/preferredTerminologyServer"
    ... value[x] 0..1 url Value of extension

    doco Documentation for this format
    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..* Extension Preferred terminology server
    ... id 0..1 id Unique id for inter-element referencing
    ... extension 0..0
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/preferredTerminologyServer"

    doco Documentation for this format

    This structure is derived from Extension

    Summary

    Simple Extension with the type url: Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the resource or a particular portion of the resource (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against (one of) the preferredTerminologyServer(s) rather than the local repository. Systems SHOULD evaluate value sets using terminology servers as follows: First, try any terminology servers declared on the element in question. If there are more then one, try them in the order they appear. Then try any servers that appear on ancestor elements in order of closest ancestor up to any on the resource root If there are no declared servers or none of the ones listed provide a useful response, the form filler may then try any of the typical servers it would normally use. A 'useful response' means a response that provides a valid (though potentially empty) expansion. Clients MAY wish to log/report errors returned by terminology servers.

    Maturity: 4

    Differential View

    This structure is derived from Extension

    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..* Extension Preferred terminology server
    ... extension 0..0
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/preferredTerminologyServer"
    ... value[x] 0..1 url Value of extension

    doco Documentation for this format

    Snapshot View

    NameFlagsCard.TypeDescription & Constraints    Filter: Filtersdoco
    .. Extension 0..* Extension Preferred terminology server
    ... id 0..1 id Unique id for inter-element referencing
    ... extension 0..0
    ... url 1..1 uri "http://hl7.org/fhir/StructureDefinition/preferredTerminologyServer"

    doco Documentation for this format

     

    Other representations of profile: CSV, Excel, Schematron

    Constraints

    IdGradePath(s)DetailsRequirements
    ele-1error**ALL** elementsAll FHIR elements must have a @value or children
    : hasValue() or (children().count() > id.count())
    ext-1error**ALL** extensionsMust 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:

    • Map the type url to uri on the element Extension.value[x]
    • 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 .. * Extension Preferred terminology server
    . . . extension 0 .. 0
    . . . url 1 .. 1 uri "http://hl7.org/fhir/StructureDefinition/preferredTerminologyServer"
    . . . value[x] 0 .. 1 uri Value of extension

    doco Documentation for this format

    Search Parameters for this Extension

    (none found)