{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "definitions": {
        "dog": {
            "type": "string",
            "pattern": "([A-Z]|[a-z])"
        }
    },
    "properties": {
        "dog": {
            "$ref": "#/definitions/dog"
        }
    },
    "required": [
        "dog"
    ]
}