Sequence Diagrams Worksheet
1. Follow the link to the IBM rational tutorial and answer the following questions:
a. What is the purpose of sequence diagrams?
b. What is a lifeline?
c. What is the difference between an alternative and an optional fragment?
2. Draw a sequence diagram for the best case scenario in the Register Student Use Case
shown below.
3.
Do a second version which uses the ALT and REF constructs to enable the extensions to be
taken into account- assume that another sequence diagram – create student – will be
written.
4. Draw a sequence diagram for the create student use case- you can also draw the robustness
diagram and other associated class diagrams.
Register Student on a module – extract from the Use Case Template
DESCRIPTION
EXTENSIONS
Step
Action
1
Student details [ id number/ name] entered
2
Full student details displayed [ address,phone no, email,
qualifications, dates]
3
List of available modules displayed [ code, title, start
date, description, minimum qualification, maximum
number]
4
Module selected
5
Availability on module checked
6
Student eligibility checked
7
Enrolment record created [student id, module id]
8
Enrolment confirmed on screen
Step
Branching Action
1a
Student not registered - create student (UC2)
5a
Module full up- offer alternative
6a
Student not eligible- offer alternative
SUB-VARIATIONS
Branching Action
1-5
Quit without saving
Create Student Use Case
DESCRIPTION
Step
Action
1
Student form displayed
2
Full student details entered [name address,phone no,
mobile number, email]
3
Student number generated and displayed, record stored
4
Any existing qualifications are added [qualifications,
grade, details]
Rough Class diagram showing entities and operations
Rough Class diagrams for interface and control classes
Robustness diagram showing classes involved.