public function update($idSite, $idNote, $date = null, $note = null, $starred = null)
    {
        $this->checkIdSiteIsLoaded($idSite);
        $this->checkNoteExists($idSite, $idNote);

        $annotation =& $this->annotations[$idSite][$idNote];
        if ($date !== null) {
            $annotation['date'] = Date::factory($date)->toString('Y-m-d');
        }
        if ($note !== null) {
            $annotation['note'] = $note;
        }
        if ($starred !== null) {
            $annotation['starred'] = $starred;
        }
    }