Several optional use cases supplement this Online Shopping System. Use Case: the customer can search for items, browse the catalog, view recommended items, and add items to the shopping cart or wish list. These use cases are extending because they include some optional functions that allow the customer to find a thing. Because both View Recommended Items and Add to Wish List require the customer to be authenticated, the Customer Authentication use case is included. Items can be added to the shopping cart without user authentication at the same time. The checkout use case contains several required use cases.