public function getAncestor($itemName, $depth = 0)
    {
        $ancestors = array();
        $parents = $this->getParents($itemName);
        if (empty($parents)) {
            $parents = $this->owner->db->createCommand()
                ->select('parent')
                ->from($this->owner->itemChildTable)
                ->where('child=:child', array(':child' => $itemName))
                ->queryColumn();
            $this->setItemParents($itemName, $parents);
        }

        foreach ($parents as $parent) {
            $ancestors[] = array(
                'name' => $parent,
                'item' => $this->owner->getAuthItem($parent),
                'parents' => $this->getAncestor($parent, $depth + 1),
                'depth' => $depth
            );
        }
        return $ancestors;
    }