{
    "type": "object",
    "properties": {
        "foo": {
            "$ref": "#/definitions/Enum"
        }
    },
    "required": [ "foo" ],
    "definitions": {
        "Enum": {
            "type": "string",
            "enum": [
                "x",
                "y"
            ]
        }
    },
    "$schema": "http://json-schema.org/draft-04/schema#"
}