1. Dynamic Modeling Grady Booch, James Rumbaugh, and Ivar Jacobson, The Unified Modeling Language User Guide, 2 nd edition, Addison Wesley, 2005.

2. 2 Outline Dynamic models State machine diagrams (a.k.a. statechart) –Modeling object or system states Interaction diagrams –Sequence diagrams (a.k.a. message sequence) The time order of interactions between objects –Communication diagrams (a.k.a. collaboration) Messages passed between objects 2

3. 3 Dynamic Models Used to model control aspects (e.g., when) Several different models possible, e.g., –Focusing on state changes –Focusing on interactions 3

4. 4 Dynamic Models Used to model control aspects (e.g., when) Several different models possible, e.g., –Focusing on state changes Used to show software control Sequence of operations and events Transitions between states UML state machine diagrams –Focusing on interactions 4

5. 5 Dynamic Models Used to model control aspects (e.g., when) Several different models possible, e.g., –Focusing on state changes –Focusing on interactions Used to show dynamic relationships between objects Messages, interfaces, and timings UML interaction diagrams –Sequence diagrams, focusing on ordered interactions –Communication diagrams, focusing on interaction links –Timing diagrams, focusing on interaction timings 5

6. 6 Outline Dynamic models State machine diagrams Interaction diagrams 6

7. 7 Modeling State Changes Modeling object/system states –UML state machine diagram –Depicts the flow of control using states and transitions by describing How an object or system changes over time Event (e.g., operation calls) it may respond to How it respond to them –Generalization of finite state machines 7

8. 8 Modeling Object States Network of states and transitions One diagram for each object with important dynamic behavior Independent timing of state machines for different objects (asynchronous) On Off switch pushed 8

9. 9 Elements of State Machine Diagrams Idle Initial State Running Final State State Transition 9

10. 10 Initial and Final States White’s turn Black’s turn black moved white moved start Black win Draw White win checkmate stalemate 10

11. 11 States Some phase during the lifetime of an object that is significant of its behavior (e.g., observable or different behavior) Condition or situation in the life of a system (or object) during which it: –Satisfies some condition (i.e., state invariant), –Performs some activity, or –Waits for some events. Set of values of properties that affect the behavior of the system (or object). –Determines response to an event –Thus, different states may produce different responses to the same event

12. 12 States (Cont.) All objects have states. A state is an abstraction of the values maintained by the object that determine behavior. Examples: –The invoice is paid. –The car is parked. –The engine is running. –Kate is working. –Jim is playing. 12

13. 13 State Corresponds to Interval of Time between Events Events: points in time State: interval of time; may correspond to a continuous activity –E.g., waiting, ringing, and flying State may be associated with value of object satisfying some condition. –E.g., automobile transmission is in reverse. –E.g., balance of account is negative 13

14. 14 Identifying States Ignore attributes that don't affect behavior Combine set of attributes that form a parameter of the control –E.g., the control is not changed by changing the digits in the phone call. 14

15. 15 Specifying States Name (optional) Internal activities (optional) –Actions and activities performed while in the state –Predefined: entry, exit, do Internal transitions (optional) –Reaction within a state but without changing state Brewing do / brew coffee pot removed/ suspend pot replaced/ resume Name Internal activities Internal transitions

16. 16 Internal Activities and Transitions Actions and activities performed while in the state –Action: atomic –Activity: more complex behavior Action/activity label, specifying triggering conditions –Entry: performed on entry to state –Exit: performed on exit from state –Do: performed while in the state Internal transitions –Reactions to events that doesn’t cause state changes (see transitions) 16 Attacking entry/unsheathe sword do/charge exit/sheathe sword enemy swings[distance<3 ft]/dodge

17. 17 Example Starting entry / start dial tone exit / end dial tone Dialing entry / number.append(n) dialed (n) [number.isValid()]

18. 18 Events Something that happens at a point in time –No duration: instantaneous –At least we think of it this way when we model (abstraction) Stimulus from one object to another May result in a change of state May result in event being sent to another object 18

19. 19 Two Events: May be unrelated (concurrent) –E.g., flight 123 departs El Paso and flight 555 departs Las Vegas. May depend on each other (sequential) –E.g., flight 123 departs El Paso and flight 123 arrives Las Vegas. 19

20. 20 Transitions Relationship between two states indicating that a system (or object) in the first state will: –Perform certain actions and –Enter the second state when specified event occurs and specified condition is satisfied. Consists of: –Source and target states –Optional event trigger, guard condition, and action Source trigger [guard] / action Target

21. 21 Transitions (Cont.) Source state –State affected by transition Event trigger –Triggering the transition Guard condition –Boolean evaluated after the event trigger. Transition only occurs if guard is true Action –Atomic operation that occurs as the transition occurs Target state –State active after transition 21 Source trigger [guard] / action Target

22. 22 Example keyPressed(key) [key == ENTER_KEY] / str := inputBuffer Note that every transition should be labeled. Source trigger [guard] / action Target 22

23. 23 Transitions (Cont.) Lead from one state to another Instantaneous Several types of events: –A condition becomes true. –An explicit signal is received from an object. –An operation is called by an object. –A designated period of time passes. 23

24. 24 Phone Example digit dialed (n) [incomplete] Dialing Connecting busy connected digit dialed (n) [valid] / connect digit dialed (n) [invalid] Invalid Ringing Busy 24

25. 25 Protocol vs. Behavior Machines Protocol state machine –Specifies the intended pattern of calls on an object by specifying which operations of the object can be called in which state and under which condition, thus specifying the allowed call sequences on the object's operations. –Describes an object's life cycle. –Post-conditions are used instead of actions Behavior state machine –Expresses the behavior of part of a system, e.g., to define object and operation behavior –Actions are used instead of post-conditions –States can have actions (entry, exit, do) 25

26. 26 Protocol State Machine 26 Not Overdrawn [balance >= 0] Overdrawn [balance < 0] credit(x) debit(x)[balance - x >= 0] credit(x)[balance + x >= 0] debit(x)[balance - x < 0]

27. 27 Protocol State Machine 27 Not Overdrawn [balance >= 0] Overdrawn [balance < 0] credit(x) debit(x)[balance - x >= 0] credit(x)[balance + x >= 0] debit(x)[balance - x < 0] Account -balance: Integer + balance(): Integer + credit(x:Integer): void + debit(x:Integer): void

28. 28 In Class: Digital Watch (Pairs) Draw a state machine diagram The watch has a single mode button and a single advance button. Pressing the mode button once and then pressing the advance button increments the hours by 1. Each press of the advance button increments the hour. Pressing the mode button the second time allows advancing the minutes by one. Pressing the mode button a third time displays the current time. While displaying the current time, the advance button is ignored. Pressing the mode button allows the user to set the hour again. 28

29. 29 In Class: Toy Train (Pairs) Draw a state machine diagram  Initially, headlight is off, and train is not moving.  If power on, headlight shines, and train moves forward.  If power off, headlight goes out, but train still moves forward.  If power on, headlight comes on, and train does not move.  If power off, headlight goes off, and train stays stopped.  If power on, headlight comes on, and train moves backward.  If power off, headlight goes off, but train still moves backward.  If power on, headlight comes on, and train doesn’t move.  If power off, headlight off, and train remains stopped.  Repeats from step 2 above.

30. 30 Structuring State Machine Diagrams anomaly Normal Recovery Identification Pressure Recovery Temperature Recovery recovery success recovery success recovery success temperature problem pressure problem recovery failure recovery failure recovery failure Can this diagram be presented better? Unstructured!

31. 31 Better Presented: anomaly Normal Recovery Identification Pressure Recovery Temperature Recovery recovery success temperature problem pressure problem Recovery recovery failure 31

32. 32 Composite States (Cont.) States containing one or more state diagrams Used to simplify diagrams Inside, looks like state machine diagrams May have composite transitions May have transitions from substates May have "history states" (H symbol) denoting the most recently occupied state Sequential (OR) and parallel (AND) states 32

33. 33 Composite States and Transitions Idle Maintenance Printing Selecting Processing Validating Transition from substate Transition to/from composite state Active 33 H Transition to history state

34. 34 Example of Composite State 34

35. 35 Including Composite States Starting entry / start dial tone exit / end dial tone Partial Dialing entry / number.append(n) dialed(n) dialedn) [number.isValid()] Dialing Dialing Number Include / Dialing 35

36. 36 Sequential (OR) and Parallel (AND) States States can be divided into concurrent parts, called “regions”. OR state: composite state with single region AND state: composite state with multiple regions –System is in all regions of the state, i.e., executes concurrently. 36

37. 37 Example of AND State 37

38. 38 Synchronization Concurrency (split of control) Synchronization substate1substate2 Superstate substate3substate4 38

39. 39 Example Idle Command Testing Waiting Diagnose Join Fork Composite state Maintaining Testing Commanding Concurrent regions 39

40. 40 Another Example HW1HW2 Incomplete Project MidtermFinal Passed Failed fail 40

41. 41 Example of Synchronization Remote Control OffOn Off Play Stop On/StopOn/Play Off On Off Off/Stop Play Stop MP3 Player 41

42. 42 In Class: Avoiding Combinatorial Explosion of States (Pairs) A car can be in the state of moving or stop. It can also be clean or dirty. Model the states of a car: without using parallel states using parallel states What will happen if we add a third property (say, Red vs. Blue) and a fourth property (say, Enclosed vs. Convertible)?

43. 43 In Class: Toy Train (Pairs) Draw a state machine diagram  Initially, headlight is off, and train is not moving.  If power on, headlight shines, and train moves forward.  If power off, headlight goes out, but train still moves forward.  If power on, headlight comes on, and train does not move.  If power off, headlight goes off, and train stays stopped.  If power on, headlight comes on, and train moves backward.  If power off, headlight goes off, but train still moves backward.  If power on, headlight comes on, and train doesn’t move.  If power off, headlight off, and train remains stopped.  Repeats from step 2 above.

44. 44 In Class: Office Phone (Pairs) Draw a state machine diagram describing the operation of an office phone. Assume that the phone has keys for the digits 0- 9, #, and *. It can detect when the receiver is on- hook or off-hook. The phone is idle when the receiver is on-hook. Model phone calls. –making calls (e.g., dialing, connecting, talking), –receiving calls (e.g., ringing, talking) 44

45. 45 Outline Dynamic models State machine diagrams Interaction diagrams 45

46. 46 Modeling Interactions Focus on communications among elements –Ordering of interactions –Messages and interfaces –Communication links –Timings of messages (between when message sent and received) 46

47. 47 UML Interaction Diagrams Whole class of diagrams including –Sequence Diagrams The time order of interactions between objects –Communication Diagrams Messages passed between objects –Interaction Overview Diagram Overview diagram that hides much of the detail –Timing Diagram Interactions with precise time axis (for real-time or time- sensitive systems) 47

48. 48 Sequence Diagrams Depicts object interaction by highlighting the time ordering of method invocations Describes a sequence of method calls among objects (This is the only interaction diagram we’ll look at.) 48

49. 49 Example message lifetime control object sdPlaceOrder 49

50. 50 Example (Cont.) Sequence of message sending 50

51. 51 Different Types of Messages 51 o: Class Synchronous message Asynchronous message Return message Creation message Destruction message >

52. 52 Return Messages sdPlaceOrder :CustomerWIndow :Customer Change Update Return (dashed line, open arrow) 52

53. 53 Creation and Destruction sdPlaceOrder :CustomerWIndow :Customer Change > getRating() > 53

54. 54 In Class: Weblog Content Management System (CMS) (Pairs) Draw a sequence diagram for creating a new blog account. The content management system allows an administrator to create a new blog account, provided the personal details of the new blogger are verified using the author credential database. A summary of the new blog account’s details should be mailed to the author. 54