 Relate Use Cases to  MVC and Application Architecture  CRC  Recap distinctions : Language, Process, Tool  Detail a Use Case  Elements of a Use Case narrative  The Use Case 'flow-of-events'  How a 'flow-of-events' and a 'scenario' differ  A Use Case 'template' Week IV (cont) Detail a Use Case

2 Detail a Use Case Write a narrative for each use case scoped for development.  Elements of a Use Case narrative.  Writing the flow-of- events.  How a flow-of-events differs from a scenario  A Use Case template

3 Sample Workflow for EU-Rent

4 Sample Use Case Diagram for EU-Rent Correct Member Details...make routine corrections or updates to a club member's changeable data (name, address, etc.). Register Club Member...record information about a new member, including setting up all the member's rental group preferences. Terminate Club Member...end a member's participation in the Customer Loyalty program.

5  Each identified Use Case is defined in further detail.  Use Case name  Use Case summary -- a brief description of: the nature of what the actor needs (the system) to do the observable result of value to the actor  Pre-conditions / Post-conditions  Use Case flow simple – bullet list more complex – "flow-of-events"  Use Case scenarios, as needed begun last time ~ refine (if needed) and then add detail for each use case The Use Case Detail

6 the set of user actions & system responses (a computation or algorithmic procedure), initiated when:  an actor signals (“sends a request to”) the system, or  the system gets a scheduled request. For example  Use Case name: Accept Bid  Use Case [initial] description: 'Accept Bid' records the amount a club member is offering in response to the invitation to bid in an auction. is refined into two thoughts:  Description: The Actor wishes to record the amount a club member is offering in response to the invitation to bid in an auction.  Goal: Upon successful completion of this processing, the system has recorded the member's bid amount. Use Case Detail ~ completing the narrative

7 Use Case Detail ~ completing the narrative (cont.)  Use Case Flow-of-Events: a narrative (outline or list) describing the sequence of action / response steps.  Use Case Scenarios: One use-case flow may have different courses of action – different paths through the flow, e.g., o different conditions o alternative branches Each scenario describes one path through the use-case flow. o one "normal" (most typical) scenario ~ generally the “Happy Day” scenario o additional variations – e.g., "what could go wrong?" If the use case is very simple, Is it okay to simply list the scenarios?

8 Use Case Detail ~ the Flow-of-Events Begin by describing the "simple" (most typical) flow:  the Accept Bid flow of events: 1. The actor enters/selects the bid to be updated. The system presents the current bid-amount for that bid, along with information on the bidder (club-member) and the auction (vehicle-model). 2. The actor visually confirms the member information. 3. The actor visually confirms the vehicle model information. 4. The actor enters the new bid-amount. The system confirms the successful update.  The pattern for each step in the flow is: The actor. The system responds with.

9 Use Case Detail ~ Scenarios A scenario is one possible path through a use-case flow. It shows one particular combination of conditions within the use case.  Begin with the typical ("happy day") case. Scenario 1: A bidder has sent in a positive-amount bid.  Then add variations (e.g., things that could go wrong). For example, you could then describe scenarios for: Scenario 2: Not active member: A bid has been sent in by a bidder who is not an active club-member. Scenario 3: Non-participating member: A bid has been sent in by a member who is not participating in the auction. Scenario 4: Bidding is closed: The auction's bidding has been closed.  However: don't go overboard during this phase. You will do more of this in later phases.

10 A Use- Case Template  Use Case Name Description Goal (Observable Result or Value)  Contract Pre-conditions & Post-conditions  Flow-of-Events Normal, Alternate, Exceptional  Scenarios (list only)  Non-Behavioral Requirements, Notes & Open Issues

12 Detail a Use Case (In Class Exercise)  Consider the Use Cases from our example of Week II (Course Registration System):  Register for courses  Select courses to teach  Request course roster  Maintain course Information  Maintain professor Information  Maintain student information  Create course catalog  We will detail the Select Courses to Teach Use Case

13 Detail a Use Case (In Class Exercise cont )  Write your use case detail in terms of what the system should do, not how the system does it, I.e., the language of the domain. It should include:  When and how the use case starts and ends  What interaction the use case has with the actors  What data is needed by the use case  The normal sequence of events for the use case  A description of any alternate or exceptional flows  Now - Detail the Select Courses to Teach Use Case

14 Detail a Use Case (In Class Workshop)  Consider Use Cases from EU-Bid