properti chang properti chang event add associ event properti equal base sourc target object clazz chang element add model facad featur clazz model pump add model event listen clazz featur properti equal featur model facad base target contain sourc add element chang element remov associ event properti equal base sourc target object clazz chang element model pump remov model event listen clazz featur properti equal featur model facad base target contain sourc remov element chang element properti chang 