As you find out more about the problem domain, you will probably find that some parts of your use cases or requirements are vague or inaccurate or do not reflect the correct terminology. UML Designer accommodates this situation; you can rename model elements and revise their contents while still preserving any links between them. Furthermore, because all models are stored in the Smalltalk repository, you can always return to a previous version.
For example, we might find out that librarians assign a new book an accession number rather than a serial number. We now need to update our Adding a new book use case, replacing the phrase "serial number" with "accession number". The new use case description should read:
A new book arrives at the library, and a librarian creates a new catalog entry with the book's author, title, and Dewey number. The catalog entry is then assigned an accession number and registered in the catalog. The catalog uses the book's Dewey number to print a bookplate and spine label for the book.
Edit the use case text to use the correct terminology and then save the new text. After you save it, select Text Editions from the pop-up menu in the hypertext pane. A browser opens showing all of the saved editions of the text of this use case; if you change your mind, you can always reload an older edition.