Based on the requirements for the library catalog system, we can identify three use cases, each describing a particular user task:
To add these use cases to the Library Catalog model, follow these steps:
A use case requires a carefully written description, rather than just a brief title. We must now use the hypertext pane (at the bottom of the Relationships Browser) to add detail to each use case. To edit the text of a use case, select the use case from the list and type the text in the hypertext pane. You can use the hypertext pane's pop-up menu to save the text, just as in any Smalltalk browser.
Add the following text to the first use case, Adding a new book to the catalog:
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 a serial number and registered in the catalog. The catalog uses the book's Dewey number to print a bookplate and spine label for the book.
When you have finished, save the text by selecting Save from the pop-up menu or pressing Ctrl+S.
Optionally, you can add descriptive text for the other use cases you created. These aren't necessary for the rest of the example, because we will focus on the Adding a new book use case.