<StructureDefinition xmlns="http://hl7.org/fhir">
  <url value="https://fhir.nhs.uk.uk/StructureDefinition/NHSDigital-Range" />
  <name value="NHSDigitalRange" />
  <status value="draft" />
  <fhirVersion value="4.0.1" />
  <kind value="complex-type" />
  <abstract value="false" />
  <type value="Range" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Range" />
  <derivation value="constraint" />
  <differential>
    <element id="Range">
      <path value="Range" />
      <constraint>
        <key value="nhsd-rng1" />
        <severity value="error" />
        <human value="If both low and high present, both should use the same units or both should have units absent" />
        <expression value="low.empty() or high.empty() or (low.unit = high.unit) or (low.unit.empty() and high.unit.empty())" />
        <source value="https://fhir.nhs.uk.uk/StructureDefinition/NHSDigital-Range" />
      </constraint>
    </element>
    <element id="Range.low.value">
      <path value="Range.low.value" />
      <min value="1" />
    </element>
    <element id="Range.high.value">
      <path value="Range.high.value" />
      <min value="1" />
    </element>
  </differential>
</StructureDefinition>