{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "definitions": {
    "yesno": {
      "enum": [
        "yes",
        "no"
      ],
      "type":"string"
    },
    "dog": {
      "properties": {
        "animal": {
          "allOf": [
            {
              "$ref":"#/definitions/yesno"
            }
          ],
          "enum": [ "yes" ]
        }
      },
      "type":"object"
    }
  }
}