public static function normalizeDataSource($dataSource, $basePath = null)
    {
        if (!empty($basePath) && !Utils::isHttpSource($dataSource)) {
            // TODO: support JSON pointers
            $absPath = $basePath.DIRECTORY_SEPARATOR.$dataSource;
            if (file_exists($absPath)) {
                $dataSource = $absPath;
            }
        }

        return $dataSource;
    }