<StructureDefinition xmlns="http://hl7.org/fhir" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hl7.org/fhir ../../publish/fhir-single.xsd">
  <id value="questionnaire-unitOption" />
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-wg">
    <valueCode value="fhir" />
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm">
    <valueInteger value="1" />
  </extension>
  <url value="http://hl7.org/fhir/StructureDefinition/questionnaire-unitOption" />
  <version value="4.6.0" />
  <name value="unitOption" />
  <status value="draft" />
  <date value="2013-07-04" />
  <publisher value="HL7" />
  <contact>
    <telecom>
      <system value="url" />
      <value value="http://www.hl7.org" />
    </telecom>
  </contact>
  <description value="A unit that the user may choose when providing a quantity value." />
  <fhirVersion value="4.6.0" />
  <mapping>
    <identity value="rim" />
    <uri value="http://hl7.org/v3" />
    <name value="RIM Mapping" />
  </mapping>
  <kind value="complex-type" />
  <abstract value="false" />
  <context>
    <type value="element" />
    <expression value="Questionnaire.item" />
  </context>
  <contextInvariant value="type='quantity'" />
  <type value="Extension" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Extension" />
  <derivation value="constraint" />
  <differential>
    <element id="Extension">
      <path value="Extension" />
      <short value="Unit choice" />
      <definition value="A unit that the user may choose when providing a quantity value." />
      <comment value="Provide either unitOption(s) or unitValueSet.  If either of the extensions are present, the units for a Quantity element are constrained to only the units listed by the extensions - i.e. it is treated as a &quot;required&quot;, not an &quot;extensible&quot; binding.  In the absence of either, any unit is valid.  See additional guidance and examples in the [SDC implementation guide](http://build.fhir.org/ig/HL7/sdc/behavior.html#unitOption)." />
      <min value="0" />
      <max value="*" />
      <mapping>
        <identity value="rim" />
        <map value="N/A (MIF-level)" />
      </mapping>
    </element>
    <element id="Extension.extension">
      <path value="Extension.extension" />
      <max value="0" />
    </element>
    <element id="Extension.url">
      <path value="Extension.url" />
      <fixedUri value="http://hl7.org/fhir/StructureDefinition/questionnaire-unitOption" />
    </element>
    <element id="Extension.value[x]">
      <path value="Extension.value[x]" />
      <min value="1" />
      <type>
        <code value="Coding" />
      </type>
    </element>
  </differential>
</StructureDefinition>