Object-oriented  analysis  (OOA)  is  a  semiformal  specification  technique  for  the object-oriented  paradigm.  Object-oriented  analysis  consists  of  three  steps.  The  first  step  is （）.  It  determines  how  the  various  results  are  computed  by  the  product  and  presents  this information in the form of a   （）    and associated scenarios. The second is   （）  ， which determines the classes and their attributes. Then determine the interrelationships and interaction among the classes. The last step is   （）  ， which determines the actions performed by or to each class or subclass and presents this information in the form of   （）  .