public function xmlOutput() {
        $o = '<?xml version="1.0" encoding="UTF-8" ?>' . "\n";
        $o.= '<XMLDB PATH="' . $this->path . '"';
        $o.= ' VERSION="' . $this->version . '"';
        if ($this->comment) {
            $o.= ' COMMENT="' . htmlspecialchars($this->comment) . '"'."\n";
        }
        $rel = array_fill(0, count(explode('/', $this->path)), '..');
        $rel = implode('/', $rel);
        $o.= '    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"'."\n";
        $o.= '    xsi:noNamespaceSchemaLocation="'.$rel.'/lib/xmldb/xmldb.xsd"'."\n";
        $o.= '>' . "\n";
        // Now the tables
        if ($this->tables) {
            $o.= '  <TABLES>' . "\n";
            foreach ($this->tables as $table) {
                $o.= $table->xmlOutput();
            }
            $o.= '  </TABLES>' . "\n";
        }
        $o.= '</XMLDB>';

        return $o;
    }