static public function getSchemaLocation($version = '2.1')
    {
        $version = Version::appendPatchVersion($version);
        
        if ($version === '2.1.0') {
            $filename = dirname(__FILE__) . '/schemes/qtiv2p1/imsqti_v2p1.xsd';
        } elseif ($version === '2.1.1') {
            $filename = dirname(__FILE__) . '/schemes/qtiv2p1p1/imsqti_v2p1p1.xsd';
        } elseif ($version === '2.2.0') {
            $filename = dirname(__FILE__) . '/schemes/qtiv2p2/imsqti_v2p2.xsd';
        } elseif ($version === '2.2.1') {
            $filename = dirname(__FILE__) . '/schemes/qtiv2p2p1/imsqti_v2p2p1.xsd';
        } else {
            $filename = dirname(__FILE__) . '/schemes/imsqti_v2p0.xsd';
        }

        return $filename;
    }