Object-oriented ysis （OOA） is a semiformal specification technique for the object-oriented paradigm. Object-oriented ysis 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（）.