During analysis, inheritance hierarchies among key abstractions (i.e., classes) are established. During design, the inheritance hierarchies are refined to
Incorporate design level classes
Incorporate chosen library classes
Analysis diagrams are reviewed to identify commonality of attributes, operations, and relationships. Superclasses are defined to hold the newly discovered commonality. This reduces the amount of code to be written and tested. It also enforces uniformity; i.e., the same item cannot be handled differently in two different classes if the two classes inherit it from a common superclass.
The final step of design for an iteration is to add the methods that every good ...