public function findByExtra( ExtraStructure $extra )
    {
        $rootId = $extra->rootParagraphId;

        return $this->createStructure( array(
            'rootId'    => $rootId,
            'extra'     => $extra,
            'rules'     => $this->getRuleMapper()
                                ->findAllByRoot(
                                    $rootId,
                                    $this->getRuleOrder()
                                ),
        ) );
    }