An Introduction to UML Interaction (Sequence and Communication) Diagrams

1. An Introduction to UML Interaction (Sequence and Communication) Diagrams Georgia State UniversityCIS 3300Spring, 2009

2. State Diagrams State Diagrams State Diagrams State Diagrams State Diagrams State Diagrams Object Diagrams Component Diagrams Class Diagrams Component Diagrams Component Diagrams Deployment Diagrams Use Case Diagrams Use Case Diagrams Scenario Diagrams Scenario Diagrams Use Case Diagrams Use Case Diagrams Scenario Diagrams Scenario Diagrams Use Case Diagrams Sequence Diagrams State Machine Diagrams Communication Diagrams A model is a complete description of a system from a particular perspective Models, Views, and Diagrams Models Activity Diagrams

3. Behavioral Diagrams Used to visualize, specify, construct, document dynamic aspects of system: • use case diagram • sequence diagram • communication diagram • state machine diagram • activity diagram

4. Diagramming Scenarios:UML ways of expressing scenarios • Activity diagrams • Several scenarios (even a full use case) at once • Similar to Petri nets, Graphcet, (concurrent) flow charts… • Interaction (sequence and communication) diagrams • Only one scenario per diagram • Involve/introduce (high level) objects • Sequence diagram • Accent on the time flow • Communication diagram • Accent on the messages between objects

5. Interaction Diagrams(Sequence and Communication) • Describe how groups of objects collaborate in some behavior • Sequence diagrams • Time-oriented • Communication diagrams • Message-oriented

6. Diagramming Scenarios:Sequence Diagrams • Describe one scenario • Involve objects and messages • Shows a number of objects and the messages that are passed between these objects. • Accent is on the time flow of events

7. Diagramming Scenarios:Sequence Diagrams • Simple scenario: We have an order and are going to invoke a command on it to calculate its price. To do that, the order needs to look at all the line items on the order and determine their prices, which are based on the pricing rules of the order’s line products. Having done that for all the line items, the order then needs to compute an overall discount, which is based on rules tied to the customer.

10. Sequence Diagrams • UML 1.0 versus UML 2.0: • Objects pass messages (UML 1.0) • Participants pass messages (UML 2.0) • Show how participants (objects) interact. • Differences in interaction styles: • Fig 4-1: Centralized, e.g. one participant does all the processing and other participants supply data. • Fig 4-2: Distributed, e.g. processing is split among many participants.

11. Bank ATM Customer « new » insert_card Session get_Customer_Information() display_menu() select_transaction(sel) « new » Transaction display_menu() quit eject_card card_returned card_taken time Diagramming Scenarios:Sequence Diagrams (cont.)

12. Interaction and Message An interaction is a behavior that comprises a set of messages, exchanged among a set of objects, to accomplish a specific purpose. A message is the specification of a communication between objects that conveys information, with the expectation that some kind of activity will ensue.

13. Sequence Diagram A sequence diagram is an interaction diagram that emphasizes the time ordering of messages. A lifeline is a vertical dashed line that represents the lifetime of an object. A focus of control is a tall, thin rectangle that shows the period of time during which an object is performing an action.

14. Sequence Diagram Notation

15. Sequence Diagram Notation

16. Sequence Diagram Notation

17. Sequence Diagram • Captures dynamic behavior (time-oriented) • Purpose • Model flow of control • Illustrate typical scenarios

19. Used during requirements analysis To refine use case descriptions to find additional objects (“participating objects”) Used during system design to refine subsystem interfaces Classes (and objects) are represented by columns Messages are represented by arrows Activations are represented by narrow rectangles Lifelines are represented by dashed lines TicketMachine Passenger UML Sequence Diagrams selectZone() insertCoins() pickupChange() pickUpTicket()

20. TarifSchedule Display Passenger selectZone() lookupPrice(selection) price displayPrice(price) UML Sequence Diagrams: Nested Messages ZoneButton Dataflow …to be continued... • The source of an arrow indicates the activation which sent the message • An activation is as long as all nested activations

21. Sequence Diagram Observations • UML sequence diagram represent behavior in terms of interactions. • Complement the class diagrams which represent structure. • Useful to find participating objects. • Time consuming to build but worth the investment.

22. Diagramming Scenarios:Communication Diagrams • Describe one scenario • Involve objects and messages • Accent is on messages exchanged between objects • Sequence and Communication diagrams are largely equivalent.

23. : Bank : Customer 4: select_transaction 3: get_customer_information 1: insert_card : ATM : Session 7: card_taken 2: « create » 6: eject_card 5: « create » : Transaction Diagramming Scenarios:Communication Diagrams(cont.)

24. Communication Diagram A communication diagram is an interaction diagram that emphasizes the organization of the objects that participate in the interaction. A path is a link between objects, perhaps with a stereotype such as «local» attached. Sequence numbers indicate the time ordering of messages, to one or more levels.

25. Communication Diagram • Captures dynamic behavior (message-oriented) • Purpose • Model flow of control • Illustrate coordination of object structure and control

26. Communication Diagram Notation

27. Communication Diagram Notation