How can we Classify the operations on classes 

This step fundamentally means all three models functional, object and dynamic (studied in last section) must be combined so that we can know what operations are to be performed on objects.

We can design a state diagram describing life history of an object. A transition is a change of the state of object and it maps into an operation on object. It helps in imagining state changes. We could associate an operation with every event received by an object. Also, sometimes an event might represent an operation on other objects too that is where one event triggers another event. Therefore, in this case, event pair must be mapped into an operation performing action and returning control provided which the events are on a single thread of control passing from one object to another object.