FHIR Chat · ValueSet ContextControl: how to read · terminology

Stream: terminology

Topic: ValueSet ContextControl: how to read

Alexander Henket (Sep 13 2017 at 18:42):

Consider this snippet:

<concept>
    <modifierExtension url="http://hl7.org/fhir/StructureDefinition/codesystem-subsumes">
        <valueCode value="AN"/>
    </modifierExtension>
    <code value="_ContextControlNonPropagating"/>
    <display value="ContextControlNonPropagating"/>
    <definition value=".."/>
    <property>
        <code value="notSelectable"/>
        <valueBoolean value="true"/>
    </property>
    <concept>
        <code value="ON"/>
        <display value="overriding, non-propagating"/>
        <definition value="..."/>
    </concept>
</concept>

According to http://hl7.org/fhir/v3/ContextControl/cs.html and RoseTree, this snippet should be read as:

_ContextControlNonPropagating subsumes AN and ON

How come ON gets its own <concept> while AN is in a modifierExtension? Is this a way to define every code once, regardless of how many places in the hierarchy it could pop-up? AN is already fully defined under _ContextControlAdditive, while ON is defined under _ContextControlNonPropagating for the first time and then called through modifierExtension under _ContextControlOverriding.

Grahame Grieve (Sep 13 2017 at 19:31):

FHIR code system syntax has a single heirarchy. The extension is a way to extend to support poly-heirarchy. It should be read as you say. The tooling serialises the first parent literally, and then uses extensions for any additional parents.

Alexander Henket (Sep 14 2017 at 20:48):

Thanks for the confirmantion

Last updated: Apr 12 2022 at 19:14 UTC