Design Problems

• Defining One-to-many Dependencies Between Objects
  • How can a one-to-many dependency between objects be defined
    without making the objects tightly coupled?
  • How can be ensured that when one object changes state
    an open-ended number of dependent objects are updated automatically?
  • How can consistency between dependent objects be maintained?
• Flexible Notification-Registration (Publish-Subscribe) Interaction
  • How can an object notify an open-ended number of other objects?
  • How can a publisher notify an open-ended number of subscribers?