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| R1 Planned |
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| R1 Implemented + R2 Planned |
 |
| R2 Implemented + R3 Planned |
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| R3 Implemented + Rx Planned |
The use case version history, use case list, and use case text for the above can be found here in a follow-up post.
Healthy systems evolve. With each release, you add the knowledge gained from the previous release and improve the next. So naturally, your use cases will reflect that. To illustrate this, take a look at the use case diagrams for a business registration system built for the Government of Samoa. Note how they progress from release to release. Note how the implemented use cases evolve from the planned.
This registration system continues to evolve. It has 21 releases so far, with 5 major releases (include several new/updated use cases). To insure the right business functionality was built, 'worked closely with the client business experts on the use cases as each major release progressed. New use cases were discovered, some existing ones updated, and others retired. This is normal for a healthy development cycle.
Note: The meat of the use cases is the text. To me, the diagrams are a visual form of the use case list: they do a nice job of listing the use cases, their actors, and functional groupings. I'm not a big fan of / nor recommend using the fancy UML include/extends/generalization constructs; it's just too easy to venture into design and forget to concentrate on the use case text.
