public function save(Doctrine_Connection $conn = null)
 {
     if (!$this->exists()) {
         $this->setCreatedAt(date('Y-m-d H:i:s'));
     }
     $modified = $this->getModified();
     if (!isset($modified['downloads']) && !isset($modified['rating'])) {
         $this->setUpdatedAt(date('Y-m-d H:i:s'));
     }
     parent::save($conn);
 }