1. Summary from previous lectures
♦ Use Case -What are the domain processes ?
Use Case Diagram
♦ Conceptual Model -What are the domain concepts, terms ?
Class Diagram (conceptual)
classes, associations, attributes

2. Fig 10.1 Summary from previous lectures

3. System Sequence Diagrams
Chapter 10
Applying UML and Patterns
-Craig Larman

4. Introduction Class diagrams represent static relationships.
Today´s lecture
Class diagrams represent static relationships.
What about modeling dynamic behavior?
Interaction diagrams(Sequence and communication diagrams) model how groups of object collaborate to perform some behavior
Typically captures the behavior of a single use case

5. System Sequence Diagram (SSD)
For a use case scenario, an SSD shows:
The System (as a black box)
The external actors that interact with System
The System events that the actors generate
SSD shows operations of the System in response to events , in temporal order
Develop SSDs for the main success scenario of a selected use case, then frequent and salient alternative scenarios
:System

6. Identifying the right Actor
In the “Process Sale” example, does the customer interact directly with the POS system?
Who does?
Cashier interacts with the system directly
Cashier is the generator of the system events

7. Fig 10.2 SSD for a Process Sale scenario

8. Relationship between SSD and Use case
System Sequence Diagrams :
♦ Draw a line representing the system as a black
box.
♦ Identify each actor that directly operates on the
system. Draw a line for each such actor.
♦ From expanded use case identify system
events that each actor generates.Illustrate them.
♦ Optionally include use case text on left.

9. Fig 10.3 Relationship between SSD and Use case

10. Naming System events & operations
System events and associated system operations should be expressed at the level of intent.
Rather than physical input medium or UI widget
Start operation names with verb (from use case)
Which is better, scanBarCode or enterItem?

11. Fig 10.4 : Naming System events & operations
Capture the intent of the operation while remaining abstract

12. Fig 10.5 SSD for ”play Monopoly” Game scenario

13. SSDs and the Glossary in parallel
Why is updating the glossary important when developing the SSD?
New terms used in SSDs may need explanation, especially if they are not derived from use cases
A glossary is less formal, easier to maintain and more intuitive to discuss with external parties such as customers

14. Why Draw SSD? Important to know the system events.
Sequence diagrams help the designer to determine how the system will react to each event.
Need to design the software to handle these events and execute a response.

15. Example 1

16. Questions ?