updat set listen base given event implement just remov listen initialis complet method effici wai dissect properti chang event adapt listen need adapt method method explain code comment method easiest implement arriv event just remov old listen inspect current model add listen need advantag need travers model structur locat initialis listen method param listen given listen param model element modelel provid notat param pce receiv event base chang updat listen properti chang listen listen object model element properti chang event pce oper pce sourc model element event properti paramet event add associ event paramet instanc event valu model add listen paramet chang type event remov associ event paramet instanc event old valu model remov listen paramet chang type end end model uml factori remov model element defin log lp log granular type statement lp log local nest statement lp log local log warn encount delet object delet model element endif clean listen listen model element initialis listen listen model element 