Use Cases

1. Use Cases Driving the Design

2. Scenarios A professor logs onto the system and is presented with a list of his/her courses. After choosing one, he/she is presented with a list of student names for which he/she provides the grades. The professor has a grade for a student who is not on the course list. He/she enters both the name and the grade of the student. A student tries to enter the grades for a course by guessing the profs password. After three tries, the system locks her/him out and notifies the system manager. Class Diagrams

3. Use Case • A collection of scenarios tied together by a common user goal. • A scenario for succesfully entering grades • Other scenarios for alternative paths • student not on list • no mark for student on list • unable to log in Class Diagrams

4. Possible Format • Primary scenario as a sequence of numbered steps • Alternatives as variations on primary sequence. Class Diagrams

5. EnterMarks Use Case 1. Log on to system 2. Select course from list of taught courses 3. Enter grade for every student on the list 4. Log out Alternative: log-on failure At step 1. Allow 3 tries, then shut down that user name and alert system manager. Class Diagrams

6. EnterMarks Use Case 1. Log on to system 2. Select course from list of taught courses 3. Enter grade for every student on the list 4. Log out Alternative: student not on list At step 3. Allow both name and grade to be entered Class Diagrams

7. EnterMarks Use Case 1. Log on to system 2. Select course from list of taught courses 3. Enter grade for every student on the list 4. Log out Alternative: no grade for student At step 3. Pick from a fixed list (e.g. ABS, NPF). Provide explanations on demand. Class Diagrams

8. Actor Use Case Using Use Cases • The UML says little about Use Case description • Does provide diagram support Class Diagrams

9. Actors • Mistranslation (from Swedish) • Think roles • Role is for the purposes of a single interaction • Same person can be multiple roles • Role can be played by multiple people • Still use actor since role has another meaning in the UML Class Diagrams

10. Use Case Description Class Diagrams

11. Use Case Relationships Class Diagrams

12. Use Case Relationships Class Diagrams

13. Use Case Relationships • Include • same behaviour across multiple use cases • Generalization • use case same as other but extra • another way of doing alternatives • Extend • like generalization, but with extension points Class Diagrams

14. Stereotypes Use Case Relationships Class Diagrams