Chapter 2: Modeling with UML - 2

1. Chapter 2: Modeling with UML - 2

2. A Medical Clinic Example “A patient calls the clinic to make an appointment for a yearly checkup. The receptionist finds the nearest empty time slot in the appointment book and schedules the appointment for that time slot” “A patient can request or discuss medication with a doctor” “A patient can make payment through the system” <includes>, <extends>, generalization Online tutorial and Use case modeling tips

3. Use Case Diagrams: Summary • Use case diagrams represent external behavior • All use cases need to be described for the model to be useful. • An Actor is a role of an object or objects outside of a system that interacts directly with it as part of a coherent work unit (a use case) • <<includes>> and <<extends>> allow common fragments of use cases to be pulled out into a separate use cases • <<includes>> is like a “use case subroutine” • <extends>> is an alternative course of action

4. zone:Zone Price: Price TarifSchedule Trip Class Diagrams • 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. Enumeration getZones() Price getPrice(Zone) * *

5. TarifSchedule TarifSchedule TarifSchedule Table zone2price Enumeration getZones() Price getPrice(Zone) zone2price getZones() getPrice() Classes Name Signature Attributes Operations • 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.

6. tarif_1974:TarifSchedule Instances 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.

7. 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”).

8. TarifSchedule TripLeg Associations Enumeration getZones() Price getPrice(Zone) PriceZone * * • Associations denote relationships between classes. • The multiplicity of an association end denotes how many objects the source object can legitimately reference.

9. 1-to-1 and 1-to-many Associations Country capital name:String name:String One-to-one association Point * Polygon x: Integer y: Integer draw() One-to-many association

10. Many-to-Many Associations Lists * * Company StockExchange tickerSymbol * 1 Lists Company StockExchange SX_ID tickerSymbol qualifier

11. From Problem Statement To Object Model Pr oblem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol Class Diagram: Company * * StockExchange Lists tickerSymbol

12. From Problem Statement to Code Pr oblem Statement : A stock exchange lists many companies. Each company is identified by a ticker Symbol Class Diagram: * * Company StockExchange Lists tickerSymbol Java Code public class StockExchange { private Vector m_Company = new Vector(); }; public class Company { public int m_tickerSymbol; private Vector m_StockExchange = new Vector(); };

13. Exhaust system TicketMachine ZoneButton 0..2 1 Muffler Tailpipe diameter diameter Aggregation Exhaust system 0..2 1 Muffler Tailpipe diameter diameter • 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. • A solid diamond denotes composition, a strong form of aggregation where components cannot exist without the aggregate. 3

14. CancelButton ZoneButton Button Inheritance • The children classes inherit the attributes and operations of the parent class. • Inheritance simplifies the model by eliminating redundancy.

15. Class Relationships Our class diagram has the following kinds of relationships. • association -- a relationship between instances of the two classes. There is an association between two classes if an instance of one class must know about the other in order to perform its work. In a diagram, an association is a link connecting two classes. • aggregation -- an association in which one class belongs to a collection. An aggregation has a diamond end pointing to the part containing the whole. In our diagram, Order has a collection of OrderDetails. • generalization -- an inheritance link indicating one class is a superclass of the other. A generalization has a triangle pointing to the superclass. Payment is a superclass of Cash, Check, and Credit.

16. Composition and aggregation • Associations in which an object is part of a whole are aggregations. Composition is a strong association in which the part can belong to only one whole -- the part cannot exist without the whole. Composition is denoted by a filled diamond at the whole end. • This diagram shows that a BoxOffice belongs to exactly one MovieTheater. Destroy the MovieTheater and the BoxOffice goes away! The collection of Movies is not so closely bound to the MovieTheater.

17. Without qualification File 1 * Directory filename With qualification 1 0…1 Directory filename File Qualifiers • Qualifiers can be used to reduce the multiplicity of an association.

18. Object Modeling in Practice: Class Identification Foo Foo, by providing his customerId, can deposit, withdraw, and get balance from his account. CustomerId Deposit() Withdraw() GetBalance() Class Identification: Name of Class, Attributes and Methods

19. Account Foo “Dada” CustomerId CustomerId CustomerId Deposit() Deposit() Deposit() Withdraw() Withdraw() Withdraw() GetBalance() GetBalance() GetBalance() Object Modeling in Practice: Encourage Brainstorming Naming is important! Is Foo the right name?

20. Account Customer Bank Name Name AccountId Deposit() Withdraw() GetBalance() Object Modeling in Practice ctd CustomerId CustomerId 1) Find New Objects 2) Iterate on Names, Attributes and Methods

21. Account Customer Bank CustomerId Name Name AccountId Deposit() AccountId CustomerId Withdraw() GetBalance() Object Modeling in Practice: A Banking System * Has 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

22. Account Amount Customer Bank CustomerId Name Name AccountId Deposit() AccountId Withdraw() GetBalance() Savings Account Checking Account Mortgage Account Withdraw() Withdraw() Withdraw() Practice Object Modeling: Iterate, Categorize! * * Has CustomerId

23. 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. • A complex system can be decomposed into subsystems, where each subsystem is modeled as a package DispatcherInterface Notification IncidentManagement

24. A Class Diagram Example • A customer order from a retail catalog. • Identify the major classes • Customer, Order • How to pay? – Payment • One order can have multiple types of merchandises. • For a merchandise, depending on its quantity, the unit price (or tax) for that order may be different….. • See Practical UML™: A Hands-On Introduction • More complex – Shipping? Stock? Account? Bank?

25. Class Diagram Summary • Class diagrams represent the structure of the system • Name, attribute, operation • Class vs. instance • Association, aggregation, composition, generalization • Multiplicity

26. 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 TicketMachine Passenger selectZone() insertCoins() pickupChange() pickUpTicket() UML sequence diagrams

27. TarifSchedule Display Passenger selectZone() lookupPrice(selection) displayPrice(price) price Nested messages ZoneButton Dataflow • 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 …to be continued...

28. CoinIdentifier Display CoinDrop Passenger insertChange(coin) lookupCoin(coin) price displayPrice(owedAmount) [owedAmount<0] returnChange(-owedAmount) Iteration & condition …continued from previous slide... ChangeProcessor * Iteration Condition • Iteration is denoted by a * preceding the message name • Condition is denoted by boolean expression in [ ] before the message name …to be continued...

29. Passenger createTicket(selection) Ticket print() free() Creation and destruction …continued from previous slide... Creation ChangeProcessor 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.

30. Sequence Diagram: A Example Making an online hotel reservation

31. 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).

32. State Chart Diagrams State Initial state Event Transition Final state Represent behavior as states and transitions

33. State Chart Diagrams -- Example A screen savor program

34. Activity Diagrams • An activity diagram shows flow control within a system • 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

35. 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 Closed Active Inactive Archived Incident- Documented Incident- Archived Incident- Handled Activity Diagram for Incident (similar to Moore (State: Operation or Collection of Operations) Triggerless Transition Completion of activity causes state transition

36. Activity Diagram: Modeling Decisions

37. Activity Diagrams: Modeling Concurrency • Synchronization of multiple activities • Splitting the flow of control into multiple threads Splitting Synchronization

38. Activity Diagrams: Swimlanes • Actions may be grouped into swimlanes to denote the object or subsystem that implements the actions. Dispatcher Allocate Resources Open Coordinate Archive Incident Resources Incident FieldOfficer Document Incident

39. 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

40. 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

41. Problems with UML • Semi-formal • Go directly to the class/objects – a low level. • Not good at express temporal information – StateChart Term paper topic for graduate students

42. Additional Slides

43. Models for Plato’s and Aristotle’s Views of Reality Plato Aristotle • Material reality is a second-class subordinate type of reality. • The first-class type is a “form” Forms lie behind every thing or in the world. Forms can be abstract nouns like “beauty” or “mammal” or concrete nouns like “tree” or “horse”. • There is an important difference between the world of forms and particulars. Forms are nonmaterial, particulars are material. Forms are permanent and changeless. Particulars are changing. • Forms can be acquired intellectually through a “dialectic” process that moves toward the highest understanding of reality through the interaction of questions and answers. • Aristotle accepted the reality of Forms as nonmaterial entities. • However, he could not accept Plato’s idea, that these Forms were not real. • Instead of two separate worlds, one for Forms and one for Particulars, Aristotle had only one world, a world of particular things. • Particular things according to Aristotle have a certain permance about them, even while they are subject to change: A tree changes colors without ceasing to be a tree. A horse grows in size without ceasing to be a horse. • What is the root of this permancence? It is the thing’s internal form, which minds detect, when they penetrate beyond the thing’s changing attributes. So for Aristotle, reality is thus made up of particular things that are each composed of form antdn matter.. Using UML, we can illustrate Platon’s and Aristotle’s viewpoints very easily and see their differences as well

44. Model for Plato’s View of Reality Plato • Material reality is a second-class subordinate type of reality. • The first-class type is a “form” Forms lie behind every thing or in the world. Forms can be abstract nouns like “beauty” or “mammal” or concrete nouns like “tree” or “horse”. • There is an important difference between the world of forms and particulars. Forms are nonmaterial, particulars are material. Forms are permanent and changeless. Particulars are changing. • Forms can be acquired intellectually through a “dialectic” process that moves toward the highest understanding of reality through the interaction of questions and answers.

45. Model Aristotle’s Views of Reality Aristotle • Aristotle accepted the reality of Forms as nonmaterial entities. • However, he could not accept Plato’s idea, that these Forms were not real. • Instead of two separate worlds, one for Forms and one for Particulars, Aristotle had only one world, a world of particular things. • Particular things according to Aristotle have a certain permance about them, even while they are subject to change: A tree changes colors without ceasing to be a tree. A horse grows in size without ceasing to be a horse. • What is the root of this permancence? It is the thing’s internal form, which minds detect, when they penetrate beyond the thing’s changing attributes. So for Aristotle, reality is thus made up of particular things that are each composed of form antdn matter..

46. Comparison of Plato’s and Aristotle’s Views Aristotle Plato