As analysis proceeds, you recognize Use Case development As analysis proceeds, you recognize commonality amongst the Use Cases that you will abstract out into common Use Cases, and complexity due to error handling and alternative flows that may be placed in extensions to the basic Use Cases There are no binding rules here, except for the one that tells you to create concise, clear, understandable, easy-to-read, and correct specifications! Why was this important? It clarified our vocabulary and It included all the parts we needed to function Discuss other ways to write use cases narrative formal scripts Sept 2002 91.3913 R. McFadyen

Use Case relationships: extends, includes, generalization Originates because of thoughts like: What could go wrong here? How might this work out differently? Includes Why was this important? It clarified our vocabulary and It included all the parts we needed to function Discuss other ways to write use cases narrative formal scripts When you have a chunk of behaviour that is similar across more than one use case and you don’t want to keep copying the description of that behaviour … use an Includes association Sept 2002 91.3913 R. McFadyen

Used to factor out behaviour to create reusable parts Use Case - Include Used to factor out behaviour to create reusable parts simplifies descriptions, but diagram becoming more complex for user comprehension a refinement where some design decision is being made Note direction of the association Extend loan BookBorrower <<include>> Check for reservation Borrow copy <<include>> Sept 2002 91.3913 R. McFadyen

Perhaps each user must be validated Use Case - Include Perhaps each user must be validated Extend loan BookBorrower <<include>> Validate user Borrow copy <<include>> Sept 2002 91.3913 R. McFadyen

Use Case - Include Process Sale Handle Cheque Payment Handle Cash Handle Credit Payment Cashier <<include>> <<include>> <<include>> Process Rental Sept 2002 91.3913 R. McFadyen

Used for “unusual” cases Use Case - Extend Used for “unusual” cases a refinement where some design decision is being made The target Use Case extends the source Use Case at a given extension point the association goes from the exceptional to the more general Main Case borrow copy BookBorrower <<extends>> Subsidiary Case refuse loan Sept 2002 91.3913 R. McFadyen

The extending Use Case points to the base Use Case Use Case - Extend The extending Use Case points to the base Use Case The condition and the extension point can be shown Base Use Case borrow copy Extension Point: Overdue Book Check BookBorrower <<extends>> borrower has overdue books Extending Use Case refuse loan Sept 2002 91.3913 R. McFadyen

Use Case Example - textual Ch 6 example. Process Sale Ch 25 example Process Rental Handle Credit Payment Handle Cheque Payment Handle Gift Certificate Payment Sept 2002 91.3913 R. McFadyen