1. Multimedia & Website Design Use Cases in UML

2. What’s Up Today? What you’ll learn in this lecture :- Use Case diagrams and their application –Why they exist –What they are –Their importance –Extending use cases –How to construct them

3. Working with the Customer Use case analysis takes place in partnership with the customer for the system Intending to discover how the planned system should be used in practical terms Should be an iterative process - first generate high level diagrams, then add detail where needed

4. What are Use Cases? Use Cases represent the users and their interaction with the system A use case model partitions functionality into ‘transactions’ that are meaningful to ‘actors’ Applications, networks and other systems are represented by boxes actor Use case Park car System

5. Why Use Cases? Use Cases are built to be simple to understand. Non technical people can interpret them with ease They provide an overview of the system diagrammatically

6. Diagram Elements Actor to initiate use case Preconditions Steps in Scenario Postconditions Actor benefiting from Use Case Use Case System Actor

7. Use Case Analysis Use Case Analysis is simply breaking down the functionality of an application into a set of diagrams It is performed by identifying areas of functionality and the users involved It’s designed to be fast and simple, and they are easily translatable from your planning

8. Use Case Relationships Use Cases have relationships between themselves and actors Very similar to Class Diagrams –Inclusion –Extension –Generalisation –Grouping

9. Inclusion Use Cases can often be used more than once, in which case they are ‘included’ eg, a car salesman and valet both need to open the car door It is the same principle as reusable operations in Classes Show Car Car Sale Open Door Clean Car Open Door > Salesman Customer > Valet

10. Extension Extensions are similar to inclusion, but instead of just reusing the code, they extend it E.g. if you make a sale on a website, you’ll register it in your own systems, and process a credit card if required Extension can only take part at specific points called Extension Points. The extension would occur after the normal Use Case Register Sale Extension point (Process credit card) Register Sale with Credit Card > Process credit card

11. Generalisation In the same way that classes inherit from each other, so can Use Cases For example, ‘Display Cars’ might be extended to ‘Display Cars on Sale’. Generalization in Use Cases are notated the same way that Class Generalization is Generalization can also occur between Actors Display Cars On Sale

12. Grouping Grouping is the collection of Use Cases into similar categories, the same way as Classes A box represents the group Group / System / Application

13. Worked Example

14. Vending Machine Look at the use case scenarios for a chocolate vending machine Work out who the actors are Understand the activities that need to take place

15. “Buy a product” use case Who is the Actor? What steps do they take? Buy a product Self service machine Customer

16. “Restock” use case Who is the Actor? What steps do they take? Restock Self service machine Supplier

17. “Collect Money” use case Who is the Actor? What steps do they take? Collect Money Self service machine Collector

18. More Detail - Inclusion Supplier and collector must both open and close the machine to accomplish their tasks Opportunity for inclusion Restock Open Machine Close Machine > Collect Money Open Machine Close Machine >

19. Restock Extension Extend Restock Fill according to sales Open Machine Close Machine > Restock Extension Point fill the compartments Restock according to sales > {Fill the compartments}

20. Generalisation In many cases, the collector and the restocker are the same person Restocker Collector Supplier’s Agent

21. Full Diagram Customer Supplier’s Agent Open Machine Close Machine > Restock Extension Point fill the compartments Restock according to sales > {Fill the compartments} Collect Money Open Machine Close Machine > Buy a Product Self Service Machine