{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "definitions": {
    "dog": {
      "allOf": [
        {
          "$ref": "#/definitions/myString"
        },
        {
          "minLength": 5,
          "maxLength": 10
        }
      ]
    },
    "myString": {
      "type": "string"
    }
  }
}