如何在活动图中实现用户可随时退出应用的设计？

Great question—sprinkling decision nodes and end nodes everywhere for an exit button gets clunky real quick, especially in large applications. Here are a few far cleaner approaches to model this functionality:

• Use an Interrupting Event (UML Standard)
  This is the most straightforward and semantically correct method. Define your exit button as a global interrupting event (like a "User Triggers Exit" signal) and attach it to the top-level activity or a major activity partition. Whenever this event is triggered—no matter which step the user is currently in—it will immediately interrupt the ongoing activity and route the flow directly to the end node. No need to add decision points to every single node; the interrupt handles the global exit behavior in one place.

• Extract a Reusable Exit Flow
  Create a dedicated sub-activity diagram or a CallBehaviorAction that encapsulates all the exit logic (like saving state, confirming with the user if needed, then terminating). Then, instead of adding exit decisions to every node, only add exit triggers to key "user interaction pause points" (e.g., main menu screens, post-operation confirmation screens). These points are where the user is most likely to initiate an exit, so linking them to your reusable exit flow cuts down on redundant nodes while still covering all realistic exit scenarios.

• Group Activities with a Partition/Expansion Region
  If your app’s activities are grouped into logical partitions (e.g., "User Management", "Content Editing"), you can attach the exit trigger to the entire partition. Any activity within that partition will respond to the exit event, allowing you to cover a whole section of your diagram with a single exit setup instead of individual nodes.

My top recommendation? Go with the interrupting event—it’s purpose-built for this exact use case, keeps your diagram uncluttered, and aligns with UML best practices.

内容的提问来源于stack exchange，提问作者InzeNL