{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "definitions": {
        "bar": {
            "type": "string"
        }
    },
    "type": "object",
    "required": [
        "foo"
    ],
    "additionalProperties": false,
    "properties": {
        "foo": {
            "$ref": "#/definitions/bar"
        }
    }
}