1. Chapter 8: Modelling Interactions and Behaviour UML Activity Diagram
Object-Oriented Software Engineering Practical Software Development using UML and Java
Chapter 8:
Modelling Interactions and Behaviour
UML Activity Diagram

2. Chapter 8: Modelling Interactions and Behaviour
Objectives
To read and write UML activity diagrams
To know when and how to use activity diagrams
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

3. What is an Activity Diagrams?
An activity diagram is like a state diagram.
Except most transitions are caused by internal events, such as the completion of a computation.
It shows actions and of control and data between them.
An activity diagram
Can be used to understand the flow of work that an object or component performs.
Can also be used to visualize the interrelation and interaction between different use cases.
Is most often associated with several classes.
One of the strengths of activity diagrams is the representation of concurrent activities.
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

4. What is the purpose of activity diagrams?
The basic purposes of activity diagrams are similar to other four diagrams; class diagram, object diagram, sequence diagram and state transition diagram. It captures the dynamic behaviour of the system.
Other four diagrams are used to show the message flow from one object to another but activity diagram is used to show message flow from one activity to another.
Activity diagram does not show any message flow from one activity to another. Activity diagram is some time considered as the flow chart. Although the diagrams looks like a flow chart but it is not.
So the purposes can be described as:
Draw the activity flow of a system.
Describe the sequence from one activity to another.
Describe the parallel, branched and concurrent flow of the system.
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

5. When to Use Activity Diagrams
The activity diagram is suitable for modeling the activity flow of the system.
An application can have multiple systems. Activity diagram also captures these systems and describes flow from one system to another.
This specific usage is not available in other diagrams. These systems can be database, external queues or any other system.
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

6. Activity Diagram symbols
(name of action)
start state
end state
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

7. Activity Diagram symbols
guard
is noted on a transition between two activities
Action 1
[guard 1]
[guard 2]
Action 2
Action 3
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

8. Activity Diagram symbols
branch
single incoming transition, several guarded outgoing transitions
[guard 1]
[guard 2]
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

9. Activity Diagram symbols
merge
multiple incoming transitions, single output
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

10. Example of branch and merge
merge node
guards
branch node
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

11. Activity Diagram symbols
fork
one incoming transitions and several outgoing transitions
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

12. Activity Diagram symbols
joint
several income transitions and one outgoing transitions (taken only when all the state on the incoming transactions have completed their activities)
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

13. Example of fork and joint
fork node
join node
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

14. Chapter 8: Modelling Interactions and Behaviour
Example 1
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

15. Example 2 – Buying Drinks from a Simple Vending Machine
Chapter 8: Modelling Interactions and Behaviour
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16. Chapter 8: Modelling Interactions and Behaviour
Swimlanes
Activity diagrams are most often associated with several classes.
The partition of activities among the existing classes can be explicitly shown using swimlanes.
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

17. Example with swimlanes – Student’s course registration
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

18. Chapter 8: Modelling Interactions and Behaviour
Exercise 1
Draw an activity diagram to show the activity of withdrawing money from the ATM machine. Include the following basic activities:-
Enter pin
Verify the pin
Withdraw the money
Print the receipt
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

19. Chapter 8: Modelling Interactions and Behaviour
Exercise 2
There is one entry gate to a parking lot, which interfaces to the APL controller through a Push-for-ticket button, a Ticket dispenser, and the Entry gate arm. When a driver enters a parking lot by pushing the Push-for-ticket button, tickets will be dispensed from a Ticket dispenser. After the driver removes the ticket, Entry gate arm will be automatically lifted.
There is also one exit gate, which interfaces to the APL controller through a Ticket reader, a Credit card reader, and the Exit gate arm. When a driver exits a parking lot by inserting the ticket into the Ticker reader, the parking fee will be computed, which uses the Credit card reader to read the card and then transfers the payment via an external Credit card banking system. When the payment has been collected, Exit gate arm will be automatically lifted.
Draw an activity diagram for the exit gate activity.
Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005

20. Chapter 8: Modelling Interactions and Behaviour
© Lethbridge/Laganière 2005