<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="observation-value-quantity" />
  <url value="http://vha.gov/fhir/StructureDefinition/observation-value-quantity" />
  <name value="observation-value-quantity" />
  <status value="draft" />
  <fhirVersion value="3.0.1" />
  <kind value="complex-type" />
  <abstract value="false" />
  <type value="Quantity" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Quantity" />
  <derivation value="constraint" />
  <differential>
    <element id="Quantity">
      <path value="Quantity" />
      <short value="A measured or measurable amount, with UCUM units of measure required " />
      <definition value="A measured amount (or an amount that can potentially be measured) used as the value of an observation that is encoded using the observation-va profile (http://vha.gov/fhir/StructureDefinition/observation-va).  This profiled data type requires the use of UCUM codes as the unit of measure" />
    </element>
    <element id="Quantity.system">
      <path value="Quantity.system" />
      <short value="UCUM" />
      <definition value="UCUM codes" />
      <min value="1" />
      <fixedUri value="http://unitsofmeasure.org" />
    </element>
  </differential>
</StructureDefinition>