object model element buffer buffer object entri action model facad entri model element object exit action model facad exit model element object action model facad activ model element entri action entri str notat util uml gener action sequenc entri action append entri append entri str action str notat util uml gener action sequenc action length append append append str exit action exit str notat util uml gener action sequenc exit action length append append exit append exit str collect internaltran model facad intern transit model element internaltran object tran internaltran length append todo good wai handl nest notat append transit notat uml tran tran notat set set 