causes for redesign

design for change

1. creating an object by specifying a class explicitly -- Abstract Factory, Factory Method, Prototype
2. dependence on specific operations Chain of Responsibilty, Command
3. dependence on hardware & software platforms -- Abstract Factory, bridge
4. dependence on object implementation or representation Abstract Factory, Bridge, Memento, Proxy
5. algorithm dependence -- Builder, Iterator, Strategy, Template Method, Visitor
6. extending functionality by subclassing -- Bridge, Chain, Composite, Decorator, Observer
7. tight coupling -- Abstract Factpry, Bridge, Chain of Responsibilities, Command, Facade, Mediator, Observer
8. inability to alter classes conveniently -- Adaptor, Decorator, Visitor