{
  "resourceType": "StructureDefinition",
  "url": "https://example.org/fhir/StructureDefinition/MyPatient",
  "name": "MyPatient",
  "status": "draft",
  "fhirVersion": "4.0.1",
  "kind": "resource",
  "abstract": false,
  "type": "Patient",
  "baseDefinition": "http://hl7.org/fhir/StructureDefinition/Patient",
  "derivation": "constraint",
  "differential": {
    "element": [
      {
        "id": "Patient",
        "path": "Patient",
        "condition": [
          "patient.birthDate"
        ],
        "constraint": [
          {
            "key": "patient-birthdate-regex",
            "severity": "error",
            "human": "Ensure patient.birthDate is a valid date within a specified range",
            "expression": "birthDate >= @1900-01-01 and birthDate < today() and birthDate.toString().matches('^(19|20)\\\\d\\\\d-(0[1-9]|1[0-2])-(0[1-9]|[12]\\\\d|3[01])$')"
          }
        ]
      },
      {
        "id": "Patient.identifier",
        "path": "Patient.identifier",
        "min": 1
      },
      {
        "id": "Patient.gender",
        "path": "Patient.gender",
        "fixedCode": "Male"
      }
    ]
  }
}