<StructureDefinition xmlns="http://hl7.org/fhir">
  <url value="https://example.org/fhir/StructureDefinition/MyModel" />
  <name value="MyModel" />
  <status value="draft" />
  <fhirVersion value="5.0.0" />
  <kind value="logical" />
  <abstract value="false" />
  <type value="https://example.org/fhir/StructureDefinition/MyModel" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Element" />
  <derivation value="specialization" />
  <differential>
    <element id="MyModel">
      <path value="MyModel" />
      <min value="0" />
      <max value="*" />
      <type>
        <code value="Element" />
      </type>
    </element>
    <element id="MyModel.email">
      <path value="MyModel.email" />
      <min value="0" />
      <max value="*" />
      <type>
        <code value="string" />
        <profile value="http://hl7.org/fhir/StructureDefinition/string" />
      </type>
      <constraint>
        <key value="email-format" />
        <severity value="error" />
        <human value="email format" />
        <expression value="^\S+@\S+\.\S+$" />
      </constraint>
    </element>
  </differential>
</StructureDefinition>