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