1. Object-Oriented Analysis & Design
Dr. M.E. Fayad, Professor
Computer Engineering Department, Room #283I
College of Engineering
San José State University
One Washington Square
San José, CA
2003
SJSU -- CmpE

2. Lesson 21: Sequence Diagrams
2003
SJSU – CmpE --- M.E. Fayad

3. 3 Lesson Objectives Understand how to generate sequence diagrams
Learn the syntax of sequence diagram
Explore examples of sequence diagrams 3
2003
SJSU – CmpE --- M.E. Fayad

4. Drawing Sequence Diagrams
Place objects that participate in the interaction at the top of the diagram, across the X-axis
Place the object that initiates the interaction at the left, and increasingly more subordinate objects to the right
Place messages the objects send and receive along the Y-axis, in order of increasing time from top to bottom 4
2003
SJSU – CmpE --- M.E. Fayad

5. Common Uses
Use sequence diagrams to model flows of control by time ordering
Do a better job of visualizing simple iteration and branching
Use collaboration diagrams to model flows of control by organization
Do a better job of visualizing complex iteration and branching and of visualizing multiple concurrent flows of control 5
2003
SJSU – CmpE --- M.E. Fayad

6. 6 Sequence Diagrams Sequence diagrams have two features:
Object lifeline
Vertical dashed line that represents the existence of an object over a period of time
Focus of control
A tall, thin rectangle that shows the period of time during which an object is performing an action, either directly or through a subordinate procedure 6
2003
SJSU – CmpE --- M.E. Fayad

7. Syntax of Sequence Diagram7
2003
SJSU – CmpE --- M.E. Fayad

8. Sequence Diagram: Example (1)8
2003
SJSU – CmpE --- M.E. Fayad

9. Sequence Diagram: Example (2)9
2003
SJSU – CmpE --- M.E. Fayad

10. Sequence Diagram: Example (3)10
2003
SJSU – CmpE --- M.E. Fayad

11. Sequence Diagram: Example (4)11
2003
SJSU – CmpE --- M.E. Fayad

12. Sequence Diagram: Example (5)12
2003
SJSU – CmpE --- M.E. Fayad

13. 13 Discussion Questions T/F:
The participants in the sequence diagrams are classes and components
The sequences in the sequence diagram are connected.
Sequence diagram is an event-trace diagram
You can generate a sequence diagram / use case.
A sequence diagram models flows of control by time ordering 13
2003
SJSU – CmpE --- M.E. Fayad