protected function getControllers() {
        $mapParentId = array();

        $acos = $this->Aco->getAll();

        // Map IDs to parent IDs
        foreach ($acos as $aco) {
            $mapParentId[$aco['ControlObject']['id']] = $aco['ControlObject']['parent_id'];
        }

        // Determine the child depth
        foreach ($acos as &$aco) {
            $depth = 0;
            $id = $aco['ControlObject']['id'];

            while (isset($mapParentId[$id])) {
                $depth++;
                $id = $mapParentId[$id];
            }

            $aco['ControlObject']['depth'] = $depth;
        }

        return $acos;
    }