<StructureDefinition xmlns="http://hl7.org/fhir">
  <meta>
    <lastUpdated value="2019-06-17T13:03:24.9051295+00:00" />
  </meta>
  <url value="http://example.org/fhir/StructureDefinition/MyExtensionSpecies" />
  <name value="MyExtensionSpecies" />
  <status value="draft" />
  <date value="2019-06-17T13:03:24.9841466+00:00" />
  <fhirVersion value="3.0.1" />
  <kind value="complex-type" />
  <abstract value="false" />
  <contextType value="resource" />
  <context value="Patient" />
  <type value="Extension" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Extension" />
  <derivation value="constraint" />
  <differential>
    <element id="Extension">
      <path value="Extension" />
      <short value="Optional Extensions Element" />
      <definition value="Optional Extension Element - found in all resources." />
      <base>
        <path value="Element" />
        <min value="0" />
        <max value="*" />
      </base>
      <constraint>
        <key value="ext-1" />
        <severity value="error" />
        <human value="Must have either extensions or value[x], not both" />
        <expression value="extension.exists() != value.exists()" />
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), 'value')])" />
      </constraint>
      <mapping>
        <identity value="rim" />
        <map value="N/A" />
      </mapping>
    </element>
    <element id="Extension.url">
      <path value="Extension.url" />
      <fixedUri value="http://example.org/fhir/StructureDefinition/MyExtensionSpecies" />
    </element>
    <element id="Extension.value[x]:valueCodeableConcept">
      <path value="Extension.valueCodeableConcept" />
      <sliceName value="valueCodeableConcept" />
      <type>
        <code value="CodeableConcept" />
      </type>
    </element>
    <element id="Extension.value[x]:valueCodeableConcept.coding.system">
      <path value="Extension.valueCodeableConcept.coding.system" />
      <type>
        <code value="uri" />
        <profile value="http://fhir.ufp/ValueSet/species" />
      </type>
    </element>
  </differential>
</StructureDefinition>