Variations on the notification strategy

• Qualified Notification: Deliver notification with enhanced semantics to inform listeners about what has changed.
• Qualified Notification Model with Subscribing: View subscribes to specific events and gets notified only when they occur.
• Passive Model: A Model without notification features.
• Lazy Model: A Model delivering its notifications on explicit request.
• Accumulator: Listens to submodels and squashes multiple notifications into a single one.
• Pre/Post notification: Deliver notifications before or after the change.
• Vetoers: Inquire listeners to approve or deny a change to occur.
• Signals: Isolate notification into a separate object.