public function updatePosition()
 {
     REST::requireRequestMethod('POST');
     $requiredParameters = array('lat', 'lon', 'friendlyname', 'identifier');
     if (Util::isValid($requiredParameters, $values, $this->params)) {
         extract($values);
         Model::detachEntity($identifier);
         if (Model::createEntity($identifier, $friendlyname, $lat, $lon)) {
             REST::sendResponse(201);
         } else {
             REST::sendResponse(500);
         }
     } else {
         REST::sendResponse(400);
     }
 }