The customer Alice visits Dog Fun to have her dog receive a NY-style puddle cut. The Dog Fun system sends a wash message to start the treatment at a cost of $10. It then sends a NY-style puddle cut message, updating the total cost to $100. Alice's visits collection is updated with the new treatment and total cost of $100.

1. SEQUENCE DIAGRAMS &
COMMUNICATION DIAGRAMS
By,
D. B. Naga Muruga,
Dept of Mechanical Engineering
Sriram Engineering College

2. Class and Object Diagrams
UML structure diagrams

3. Interaction Diagrams
• Describe how objects collaborate to achieve some behavior

4. Consider a use case
• We have an order
• We are going to calculate its price
• Order needs to look at all its line items
– determine price of line item based on the pricing rules of its
product

6. Another sequence diagram of the use case

7. Creating and deleting participants

8. Interaction Frames
• Sequence diagrams are not suitable for
showing complex control flow
• Instead use
– pseudocode
– activity diagrams
• Use interaction frames to describe simple
control logic

9. Format of interaction frames

10. Example

12. Control logic in UML 1
• Iteration marker (*) on message
– iteration basis given in “[]”
• Guards
– message conditions in “[]”
• Problem: only works on a single message
– Solution: use self-call by a pseudo message
to show scope

14. Synchronous and Asynchronous
messages
• Synchronous
– The sender object must wait for the receiver
object to finish
– symbol UML 2 UML <1.4
• Asynchronous
– The sender object can carry on without
waiting
– symbol UML 2 UML <1.4

15. Communication Diagrams
• Focus on the data links between objects
• Communication diagrams are graphs
– Nodes: Objects
– Edges: Association and transient links
messages are arrows on links
• Communication sequence given by
numbering scheme

16. Centralized pricing example

17. Centralized pricing example

18. Other conventions
• You can show several computations in one
diagram
– 1.1, 1.2.1, 1.2.2, 1.3, …
– 2.1, 2.2, 2.3.1, 2.3.2,…
• You can use letters to indicate different threads
– A1.1, A1.2.1, A1.2.2,…
– B1.1, B1.2.1, B1.2.2,…
• You can use iteration markers “*” and guards []
to show control logic, but no complete constructs

19. • A matter of personal taste
• Sequence diagrams better when you want
to emphasize sequence of calls
• Communication diagrams better when you
want to emphasize links
How to choose between sequence
and communication diagrams

20. Dog Fun
• Each customer has one or more dogs
• I keep track of the customers’ kind of dogs and email so I can send them greetings at
Christmas and new offers
[if they want]. I also keep track of how much they have spent
• The system helps me compute how much the customer should pay for the treatments
of the dogs the customer
brings
• A treatment starts with a wash that has a fixed cost of 10$ no matter what kind of dog
• Then there are three kinds of ways to continue a
treatment:
1. puddle-cut which can be NY-style to $100 or London to $50
(London style may include coloring for an extra $10) [I decline to puddle cut a dog that’s not a puddle]
2. trim-cut for $30, or
3. style-cut for $40
• Some of my costumers get a discount of some percent, but not all

21. Alice visits Dog Fun to have her dog in for a NY-style cut.
Show how the visits collection of Alice is updated.