{
  "$id": "https://example.com/citizen.schema.json",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Citizen",
  "type": "object",
  "properties": {
    "firstName": {
      "type": "string",
      "description": "The citizen's first name."
    },
    "lastName": {
      "type": "string",
      "description": "The citizen's last name."
    },
    "age": {
      "description": "Age in years which must be equal to or greater than zero.",
      "type": "integer",
      "minimum": 0
    },
    "city": {
      "$ref": "city.json"
    }
  }
}