"Rectangle": {
  "type": "object",
  "additionalProperties": false,
  "title": "Rectangle",
  "description": "A rectangle defined by area in square metres and aspect ratio.",
  "required": [
    "Area",
    "AspectRatio"
  ],
  "properties": {
    "Area": {
      "type": "number",
      "title": "Area"
    },
    "AspectRatio": {"$ref": "#/definitions/AspectRatio"}
  }
}

 "Area": {
  "type": "number",
  "title": "Area"
}

 "AspectRatio": {"$ref": "#/definitions/AspectRatio"}