public function setAttributeNS($namespace_uri, $qname, $value)
    {
        $localname = preg_replace('/^[^:]*:/', '', $qname);
        if (!($n = $this->getAttributeNodeNS($namespace_uri, $localname))) {
            $this->attribute_nodes[] = $n = new PHPTAL_Dom_Attr($qname, $namespace_uri, null, 'UTF-8'); // FIXME: find encoding
        }
        $n->setValue($value);
    }