Chapter 2, Modeling with UML

Transcription

1 Chapter 2, Modeling with UML Using UML, Patterns, and Java Object-Oriented Software Engineering

2 Overview: Modeling with UML What is modeling? What is UML? Use case diagrams Class diagrams Next lecture Sequence diagrams Activity diagrams Then Apply UML to Appalcart Project Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2

3 What is modeling? Modeling consists of building an abstraction of reality. Abstractions are simplifications because: They ignore irrelevant details and They only represent the relevant details. What is relevant or irrelevant depends on the purpose of the model. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 3

4 Example: Appalcart route Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 4

5 Why model software? Software is getting increasingly more complex Windows XP > 40 million lines of code A single programmer cannot manage this amount of code in its entirety. Code is not easily understandable by developers who did not write it We need simpler representations for complex systems Modeling is a mean for dealing with complexity Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 5

6 Systems, Models and Views A model is an abstraction describing a subset of a system A view depicts selected aspects of a model A notation is a set of graphical or textual rules for depicting views Views and models of a single system may overlap each other Examples: System: Aircraft Models: Flight simulator, scale model Views: All blueprints, electrical wiring, fuel system Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 6

7 Systems, Models and Views Aircraft System Blueprints Model 1 View 1 Flightsimulator Model 2 View 2 View 3 Scale Model Electrical Wiring Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 7

8 Models, Views and Systems (UML) System * Model * View Described by Depicted by Airplane: Syste m Scale Model: Model Flight Simulator: Model Blueprints: View Fuel System: View Electrical Wiring: View Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 8

9 Concepts and Phenomena Phenomenon An object in the world of a domain as you perceive it Example: The lecture you are attending Example: My watch with a heart-rate monitor Concept Describes the properties of phenomena that are common. Example: Lectures on software engineering Example: All watches with a heart-rate monitor Concept is a 3-tuple: Name (To distinguish it from other concepts) Purpose (Properties that determine if a phenomenon is a member of a concept) Members (The set of phenomena which are part of the concept) Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 9

10 Concepts and phenomena Name Purpose Members Clock A device that measures time. Abstraction Classification of phenomena into concepts Modeling Development of abstractions to answer specific questions about a set of phenomena while ignoring irrelevant details. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 10

11 Concepts in software: Type and Instance Type: An abstraction in the context of programming languages Name: int, Purpose: integral number, Members: 0, -1, 1, 2, -2,... Instance: Member of a specific type The type of a variable represents all possible instances the variable can take The following relationships are similar: type < > instance concept < > phenomenon Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 11

12 Abstract Data Types & Classes Abstract data type Special type whose implementation is hidden from the rest of the system. Class: An abstraction in the context of objectoriented languages Like an abstract data type, a class encapsulates both state (variables) and behavior (methods) Class ArrayList Unlike abstract data types, classes can be defined in terms of other classes using inheritance time date Watch SetDate(d) CalculatorWatch calculatorstate EnterCalcMode() InputNumber(n) Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 12

13 Application and Solution Domain Application Domain (Requirements Analysis): The environment in which the system is operating Solution Domain (System Design, Object Design): The available technologies to build the system Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 13

14 What is UML? UML (Unified Modeling Language) An emerging standard for modeling object-oriented software. Resulted from the convergence of notations from three leading object-oriented methods: OMT (James Rumbaugh) OOSE (Ivar Jacobson) Booch (Grady Booch) Reference: The Unified Modeling Language User Guide, Addison Wesley, Supported by several CASE tools Rational ROSE TogetherJ Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 14

15 UML: First Pass You can model 80% of most problems by using about 20 % UML We teach you those 20% Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 15

16 UML First Pass Use case diagrams Describe the functional behavior of the system as seen by the user. Class diagrams Describe the static structure of the system: Objects, Attributes, Associations Sequence diagrams Describe the dynamic behavior between actors and the system and between objects of the system Statechart diagrams Describe the dynamic behavior of an individual object (essentially a finite state automaton) Activity diagrams Model the dynamic behavior of a system, in particular the workflow (essentially a flowchart) Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 16

17 UML first pass: Use case diagrams Package Watch Use case Actor ReadTim e WatchUser SetTime W atchrepairperson ChangeBattery Use case diagrams represent the functionality of the system from user s point of view Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 17

18 UML first pass: Class diagrams Class diagrams represent the structure of the system Association Class Multiplicity Watch PushButton state push() release() 1 LCDDisplay blinkidx blinkseconds() blinkminutes() blinkhours() stopblinking() referesh() 2 Battery load 1 Ti me now Attribute Operations Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 18

19 UML first pass: Sequence diagram Actor Object :WatchUser :Watch :LCD Display :Time pressbutton1() blinkhours() Message pressbutton1() pressbutton2() blink Minutes() incrementminutes() refresh() pressbuttons1and2() co m mitnewtime() stopblinking() Activation Lifeline Sequence diagrams represent the behavior as interactions Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 19

20 UML first pass: Statechart diagrams for objects with interesting dynamic behavior Event Initial state State [button1&2pressed] BlinkHours [button2pressed] IncrementHrs Transition [button1pressed] [button1&2pressed] BlinkMinutes [button2pressed] IncrementMin. [button1pressed] [button1&2pressed] [button2pressed] BlinkSeconds IncrementSec. StopBlinking Final state Represent behavior as states and transitions Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 20

21 Other UML Notations UML provide other notations that we will be introduced in subsequent lectures, as needed. Implementation diagrams Component diagrams Deployment diagrams Introduced in lecture on System Design Object constraint language Introduced in lecture on Object Design Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 21

22 UML Core Conventions Rectangles are classes or instances Ovals are functions or use cases Instances are denoted with an underlined names m y W a tch:sim plew atch Joe:Firefighter Types are denoted with non underlined names Simple Watch Firefighter Diagrams are graphs Nodes are entities Arcs are relationships between entities Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 22

23 Use Case Diagrams Used during requirements elicitation to represent external behavior Passenger PurchaseTicket Actors represent roles, that is, a type of user of the system Use cases represent a sequence of interaction for a type of functionality The use case model is the set of all use cases. It is a complete description of the functionality of the system and its environment Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 23

24 Actors Passenger An actor models an external entity which communicates with the system: User External system Physical environment An actor has a unique name and an optional description. Examples: Passenger: A person in the train GPS satellite: Provides the system with GPS coordinates Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 24

25 Use Case A use case represents a class of functionality provided by the system as an event flow. PurchaseTicket A use case consists of: Unique name Participating actors Entry conditions Flow of events Exit conditions Special requirements Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 25

26 Use Case Diagram: Example Name: Purchase ticket Participating actor: Passenger Entry condition: Passengerstanding in front of ticket distributor. Passengerhas sufficient money to purchase ticket. Event flow: 1. Passengerselects the number of zones to be traveled. 2. Distributor displays the amount due. 3. Passengerinserts money, of at least the amount due. 4. Distributor returns change. 5. Distributor issues ticket. Exit condition: Passengerhas ticket. Anything missing? Exceptional cases! Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 26

27 The <<extends>> Relationship Passenger PurchaseTicket <<extends>> <<extends>> <<extends>> relationships represent exceptional or seldom invoked cases. The exceptional event flows are factored out of the main event flow for clarity. Use cases representing exceptional flows can extend more than one use case. The direction of a <<extends>> relationship is to the extended use case <<extends>> O utoforder <<extends>> TimeOut Cancel NoChange Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 27

28 The <<includes>> Relationship Passenger PurchaseSingleTicket <<includes>> PurchaseMultiCard <<includes>> <<includes>> relationship represents behavior that is factored out of the use case. <<includes>> behavior is factored out for reuse, not because it is an exception. The direction of a <<includes>> relationship is to the using use case (unlike <<extends>> relationships). <<extends>> CollectMoney <<extends>> NoChange Cancel Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 28

29 Use Case Diagrams: Summary Use case diagrams represent external behavior Use case diagrams are useful as an index into the use cases Use case descriptions provide meat of model, not the use case diagrams. All use cases need to be described for the model to be useful. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 29

30 Class Diagrams TarifSchedule Enumeration getzones() Price getprice(zone) * * Trip zone:zone Price: Price Class diagrams represent the structure of the system. Used during requirements analysis to model problem domain concepts during system design to model subsystems and interfaces during object design to model classes. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 30

31 Classes TarifSchedule zone2price getzones() getprice() Name Attributes Operations TarifSchedule Table zone2price Enumeration getzones() Price getprice(zone) Signature TarifSchedule A class represent a concept A class encapsulates state (attributes) and behavior (operations). Each attribute has a type. Each operation has a signature. The class name is the only mandatory information. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 31

32 Instances tarif_1974:tarifschedule zone2price = { { 1,.20}, { 2,.40}, { 3,.60}} An instance represents a phenomenon. The name of an instance is underlined and can contain the class of the instance. The attributes are represented with their values. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 32

33 Actor vs Instances What is the difference between an actor, a class and an instance? Actor: An entity outside the system to be modeled, interacting with the system ( Passenger ) Class: An abstraction modeling an entity in the problem domain, must be modeled inside the system ( User ) Object: A specific instance of a class ( Joe, the passenger who is purchasing a ticket from the ticket distributor ). Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 33

34 Associations TarifSchedule Enumeration getzones() Price getprice(zone) * * TripLeg Price Zone Associations denote relationships between classes. The multiplicity of an association end denotes how many objects the source object can legitimately reference. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 34

35 1-to-1 and 1-to-many Associations Country name:string Has-capital City name:string One-to-one association Polygon draw() * Point x: Integer y: Integer One-to-many association Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 35

36 Many-to-Many Associations StockExchange * Lists * Company tickersymbol StockExchange * Lists 1 tickersymbol SX_ID Company Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 36

37 From Problem Statement To Object Model Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol. A company may be listed on more than one stock exchange. Class Diagram: StockExchange * Lists * Company tickersymbol Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 37

38 From Problem Statement to Code Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol. A company may be listed on more than one stock exchange. Class Diagram: StockExchange * Lists * Company tickersymbol Java Code public class StockExchange { private ArrayList m_company = new ArrayList(); }; public class Company { public int m_tickersymbol; private ArrayList m_stockexchange = new ArrayList(); }; Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 38

39 Aggregation An aggregation is a special case of association denoting a consists of hierarchy. The aggregate is the parent class, the components are the children class. Exhaust system Muffler diameter Tailpipe diameter A solid diamond denotes composition, a strong form of aggregation where components cannot exist without the aggregate. (Bill of Material) TicketM achine 3 ZoneButton Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 39

40 Figure 2-7, Example of describing a model with two different notations. UML Book 1 * Chapter composed-of Booch Book composed-of N Chapter Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 40

41 Qualifiers Without qualification Directory 1 * File filenam e With qualification Directory filenam e File Qualifiers can be used to reduce the multiplicity of an association. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 41

42 Inheritance Button CancelButton ZoneButton The children classes inherit the attributes and operations of the parent class. Inheritance simplifies the model by eliminating redundancy. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 42

43 Object Modeling in Practice: Class Identification Foo Amount CustomerId Deposit() Withdraw() GetBalance() Class Identification: Name of Class, Attributes and Methods Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 43

44 Object Modeling in Practice: Encourage Brainstorming Dada Amount CustomerId Deposit() Withdraw() GetBalance() Foo Amount CustomerId Deposit() Withdraw() GetBalance() Account Amount CustomerId Naming is important! Is Foo the right name? Deposit() Withdraw() GetBalance() Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 44

45 Object Modeling in Practice Account Bank Name Amount CustomerId AccountId Deposit() Withdraw() GetBalance() Customer Name CustomerId 1) Find New Objects 2) Iterate on Names, Attributes and Methods Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 45

46 Object Modeling in Practice: A Banking System Account Bank Name Amount CustomerId AccountId Deposit() Withdraw() GetBalance() * Has Customer Name CustomerId 1) Find New Objects 2) Iterate on Names, Attributes and Methods 3) Find Associations between Objects 4) Label the assocations 5) Determine the multiplicity of the assocations Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 46

47 Practice Object Modeling: Iterate, Categorize! Bank Name * Account Amount CustomerId AccountId * Has Customer Name Deposit() Withdraw() GetBalance() CustomerId() Savings Account Checking Account Mortgage Account Withdraw() Withdraw() Withdraw() Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 47

48 Watch time date SetDate(d) CalculatorWatch calculatorstate EnterCalcMode() InputNumber(n) Figure 2-8, A UML class diagram depicting two classes: Watch and CalculatorWatch. CalculatorWatch is a refinement of Watch, providing calculator functionality normally not found in normal Watches. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 48

49 Figure 2-9, An example of abstract class. OrganicCompound Benzene Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 49

50 Figure 2-10, A UML class diagram depicting instances of two classes. simplewatch1291:watch «instanceof» Watch calculatorwatch1515 :CalculatorWatch «instanceof» CalculatorWatch Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 50

51 Packages A package is a UML mechanism for organizing elements into groups (usually not an application domain concept) Packages are the basic grouping construct with which you may organize UML models to increase their readability. DispatcherInterface Notification IncidentManagem ent A complex system can be decomposed into subsystems, where each subsystem is modeled as a package Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 51

52 UML sequence diagrams TicketMachine Passenger selectzone() insertcoins() pickupchange() pickupticket() Used during requirements analysis To refine use case descriptions to find additional objects ( participating objects ) Used during system design to refine subsystem interfaces Classes are represented by columns Messages are represented by arrows Activations are represented by narrow rectangles Lifelines are represented by dashed lines Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 52

53 Nested messages Passenger selectzone() ZoneButton TarifSchedule Display lookupprice(selection) price Dataflow displayprice(price) to be continued... The source of an arrow indicates the activation which sent the message An activation is as long as all nested activations Horizontal dashed arrows indicate data flow Vertical dashed lines indicate lifelines Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 53

54 Iteration & condition continued from previous slide... ChangeProcessor CoinIdentifier Display CoinDrop Passenger * insertchange(coin) lookupcoin(coin) Iteration price displayprice(oweda mount) Condition [owedamount<0]returnchange(-oweda mount) to be continued... Iteration is denoted by a * preceding the message name Condition is denoted by boolean expression in [ ] before the message name Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 54

55 Creation and destruction continued from previous slide... Passenger ChangeProcessor createticket(selection) Creation print() Ticket free() Destruction Creation is denoted by a message arrow pointing to the object. Destruction is denoted by an X mark at the end of the destruction activation. In garbage collection environments, destruction can be used to denote the end of the useful life of an object. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 55

56 Sequence Diagram Summary UML sequence diagram represent behavior in terms of interactions. Useful to find missing objects. Time consuming to build but worth the investment. Complement the class diagrams (which represent structure). Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 56

57 State Chart Diagrams Event Initial state State [button1&2pressed] BlinkHours [button2pressed] IncrementHrs Transition [button1pressed] [button1&2pressed] BlinkMinutes [button2pressed] IncrementMin. [button1pressed] [button1&2pressed] [button2pressed] BlinkSeconds IncrementSec. StopBlinking Final state Represent behavior as states and transitions Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 57

58 Group Work The following sequence of diagrams are taken from an example developed in the textbook. We will review UML notation by trying to understand these diagrams. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 58

59 Figure 2-13, An example of a UML use case diagram: Incident initiation in an accident management system. FRIEND Report Emergency FieldOfficer OpenIncident Dispatcher AllocateResources Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 59

60 Figure 2-16, An example of an «include» relationship. OpenIncident «include» AllocateResources «include» HelpDispatcher Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 60

61 Figure 2-18, An example of an «extend» relationship. OpenIncident «extend» AllocateResources «extend» ConnectionDown Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 61

62 Figure 2-22, An example of a UML class diagram: classes that participate in the ReportEmergency use case. EmergencyReport reportsgenerated * FieldOfficer reports 1..* 1 Incident * incidentsgenerated Dispatcher name:string badgenumber:integer 1 author name:string badgenumber:integer 1 initiator Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 62

63 Figure 2-23, An example of a UML object diagram: objects that participate in the warehouseonfire scenario. bob:fieldofficer report_1291 incident_1515 name = Bob D. badgenumber = 132 alice:fieldofficer name = Alice W. badgenumber = 23 john:dispatcher name = John D. badgenumber = 12 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 63

64 Figure 2-25, An example of an association class. Allocates FieldOfficer role:string notificationtime:time Incident name:string badgenumber:integer resources 1..* 1 incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 64

65 Figure 2-26, Alternative model for Allocation. FieldOfficer name:string badgenumber:integer 1 1..* resources Allocation role:string notificationtime:time 1 incident 1 Incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 65

66 Figure 2-32, An example of a generalization. PoliceOfficer name:string badgenumber:integer FieldOfficer author Dispatcher 1 * reportsgenerated EmergencyReport 1..* initiator 1 * incidents 1 Incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 66

67 IncidentManagement Report Emergency OpenIncident Dispatcher FieldOfficer AllocateResources IncidentArchive SysAdministration ArchiveIncident ManageUsers Librarian SearchArchive ManageTerminals Figure 2-45, Example of packages: use cases of FRIEND organized by actors. SysAdmin Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 67

68 Figure 2-46, Example of packages. FieldOfficer IncidentManagement Dispatcher Librarian IncidentArchive SysAdministration SysAdmin Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 68

69 Figure 2-47, Example of packages. FieldStation DispatcherStation FieldOfficer Dispatcher EmergencyReport Incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 69

70 Figure 2-48, An example of a note. Notes can be attached to a specific element in a diagram. FieldStation DispatcherStation FieldOfficer Dispatcher EmergencyReport The EmergencyReport class is defined in FieldStation and used in both stations. Incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 70

71 Activity Diagrams An activity diagram shows flow control within a system Handle Incident Document Incident Archive Incident An activity diagram is a special case of a state chart diagram in which states are activities ( functions ) Two types of states: Action state: Cannot be decomposed any further Happens instantaneously with respect to the level of abstraction used in the model Activity state: Can be decomposed further The activity is modeled by another activity diagram Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 71

72 Statechart Diagram vs. Activity Diagram Statechart Diagram for Incident (similar to Mealy Automaton) (State: Attribute or Collection of Attributes of object of type Incident) Event causes State transition Active Inactive Closed Archived Incident- Incident- Incident- Handled Docu mented Archived Activity Diagram for Incident (similar to Moore (State: Operation or Collection of Operations) Handle Incident Document Incident Archive Incident Completion of activity causes state transition Triggerless Transition Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 72

73 Activity Diagram: Modeling Decisions Open Incident [lowpriority] [fire & highpriority] Allocate Resources [not fire & highpriority] Notify Fire Chief Notify Police Chief Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 73

74 Activity Diagrams: Modeling Concurrency Synchronization of multiple activities Splitting the flow of control into multiple threads Splitting Allocate Resources Synchronization Open Incident Coordinate Resources Archive Incident Document Incident Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 74

75 Activity Diagrams: Swimlanes Actions may be grouped into swimlanes to denote the object or subsystem that implements the actions. Allocate Resources Dispatcher Open Incident Coordinate Resources Archive Incident Document Incident FieldOfficer Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 75

76 What should be done first? Coding or Modeling? It all depends. Forward Engineering: Creation of code from a model Greenfield projects Reverse Engineering: Creation of a model from code Interface or reengineering projects Roundtrip Engineering: Move constantly between forward and reverse engineering Useful when requirements, technology and schedule are changing frequently Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 76

77 UML Summary UML provides a wide variety of notations for representing many aspects of software development Powerful, but complex language Can be misused to generate unreadable models Can be misunderstood when using too many exotic features For now we concentrate on a few notations: Functional model: Use case diagram Object model: class diagram Dynamic model: sequence diagrams, statechart and activity diagrams Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 77