Use Case description

1. Asper School of Business University of Manitoba Systems Analysis & Design Instructor: Bob Travica Use Case description Updated: October 2013

2. Outline • Concept of Use Case Description • Levels of Use Case Description • Reading and writing Use Case Descriptions 3510 Systems Analysis & Design * Bob Travica

3. Use Case Diagram of the Customer Support System Use Cases grouped into system modules Maintain Catalog Note: Same actor interacts with different modules 3510 Systems Analysis & Design * Bob Travica

4. Use Case Description • Complements Use Case Diagram • A breakdown of a single use case (e.g., sequence of steps included in the function “Look up item availability”); process logic included • In contrast to Use Case Diagram, Use Case Description captures variations of a Use Case • Example: “Create new order” can be done via phone+clerk and via Internet ordering – 2 scenarios 3510 Systems Analysis & Design * Bob Travica

5. * UC=Use Case Level of Use Case Description • Three levels of detail: • UC* Brief description • Summary of what system does in response to actor’s actions • UC Intermediate description • Shows steps in use case, if-then • UC Full description • Includes Brief description, expands intermediate description, shows scenarios 3510 Systems Analysis & Design * Bob Travica

6. Brief Description of Create New Order Use Case • Same description that is usually captured in initial Use Case Diagrams (“bird’s view” of system) 3510 Systems Analysis & Design * Bob Travica

7. Intermediate Use Case Description Telephone Order Scenario for Create New Order Use Case 3510 Systems Analysis & Design * Bob Travica

8. Full Use Case Description • Superset of intermediate and brief descriptions (contains these) • Consists of 11 compartments (we will use some) • Shows steps (“Flow of Events”) broken down to the actor and the system side – useful! 3510 Systems Analysis & Design * Bob Travica

9. Full Use Case Description Telephone Order Scenario for Create New Order Use Case Computer System, Computer (steps encoded in software) 3510 Systems Analysis & Design * Bob Travica

10. Reading and Writing Use Case Descriptions • Reading: Straightforward • Writing: • We will not use it much • Useful to practice because it leads to other modeling techniques (activity diagram, class diagram) 3510 Systems Analysis & Design * Bob Travica

11. Writing Use Case Descriptions • Select a use case • Write abbreviated full description (Use case name, Scenario (if any), Business Event, Actors, Flow of steps, Exception conditions) • For figuring Flow of steps, - Keep in mind general system model: Input-Processing-Output - Steps should be at nearly the same level of abstraction (each makes nearly same progress toward use case completion) • For figuring exception conditions, focus on if-then logic. 3510 Systems Analysis & Design * Bob Travica