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 determines 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 　（）.