public function addReadableModel($id) {
    
        common_Logger::i('ADDING MODEL '.$id);
    
        $readables = $this->getOption(self::OPTION_READABLE_MODELS);
        $this->setOption(self::OPTION_READABLE_MODELS, array_unique(array_merge($readables, array($id))));
    
        // update in persistence
        ModelManager::setModel($this);
    }