private function getAnnotationsForSite()
    {
        $result = array();
        foreach ($this->idSites as $id) {
            $optionName = self::getAnnotationCollectionOptionName($id);
            $serialized = Option::get($optionName);

            if ($serialized !== false) {
                $result[$id] = Common::safe_unserialize($serialized);
                if (empty($result[$id])) {
                    // in case unserialize failed
                    $result[$id] = array();
                }
            } else {
                $result[$id] = array();
            }
        }
        return $result;
    }