param elem uml element delet delet classifi role object elem classifi role cr classifi role elem delet messag sender receiv collabor pkg omg uml uml cr ref outermost collabor model impl uml helper delet collect pkg messag sender messag cr model impl uml helper delet collect pkg receiv messag messag cr todo delet collabor classifi role object owner cr ref immedi composit owner collabor collect own element collabor owner own element own element size own element contain cr nsmodel uml factori delet owner 