Observer

1. Describe the participant collaborations in an observer pattern
2. Specify the flow of information causing an update cycle
3. Specify how classes in the Java JDK can be used to implement an Observer pattern
4. Explain issues in C++ with maintenance of references by subject in Observer pattern
5. Describe the tradeoff between "push" and "pull" updates
6. Describe mechanisms for reducing the number of update cycles in systems with heavy change activity