protected function parseSchema($data, $key)
    {
        $this->parseDefined($key);

        if (array_key_exists(self::REQUIRED_KEY, $data)) {
            $this->parseRequired(
                $key,
                $data[self::REQUIRED_KEY]
            );
        }

        if (array_key_exists(self::DEFAULT_VALUE, $data)) {
            $this->parseDefault(
                $key,
                $data[self::DEFAULT_VALUE]
            );
        }
    }