public function sendPresence($to, $from = NULL, $type = NULL) {
		$type = is_null($type) ? '' : " type=\"{$type}\"";
		return $this->send('<presence to="' . htmlspecialchars($to) . '" from="' . (is_null($from) ? $this->component_name : htmlspecialchars("$from@{$this->component_name}")) . '"' . $type . ' />');
	}