1Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 293DesignMethodsPatternsObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 294MethodConceptsNotationsProcessHeuristics(a book)Method: A systematicway of doingsomething.2Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 295Responsibility Driven DesignConceptsClassResponsibilityCollaborationInheritanceSubsystemContractsBook: Object-Oriented Design byWirfs-Brock,Wilkerson andWienerObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 296Object Modeling Technique (OMT)ConceptsObjectsClassesAssociations /CardinalityAttributesInheritanceEventsBook: Object-Oriented Modelingand Designby Rumbaugh, Blaha,Premerlani, Eddy andLorenson3Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 297UMLUnified Modeling LanguageBooch, Rumbaugh, JacobsonUML = concepts and notationUnified Process = UML + a processObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 298Objects and AssociationsJohn is Mary’s father. Mary is John’sdaughter.Bob is Mary’s dog. Mary is Bob’s owner.Ann is John’s employer. John is Ann’semployee.4Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 299Objects and AssociationsMaryJohnBobAnnchild fatheremployeeemployerownerpetObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 300Classes and AssociationsPersonDogAnimalchildfatheremployeeemployerownerpet5Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 301Objects and AttributesJohn’s name is "John PatrickO’Brian".John’s age is 27.John’s address is 987 N. Oak St,Champaign IL 61820What about John’s employer?John’s wife?Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 302Objects and AttributesJohnname: "John Patrick O’Brian"age: 27address: ...6Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 303Objects and BehaviorJohn can earn money by working for hisemployer.John fills out time-cards.John takes vacations.Employer gives John a paycheck.John spends money to gain morepossessions.Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 304fill out time-cardstake vacationsreceive paycheckbuy/spendmake reservationstravelcheck inJohn7Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 305Event DiagramsPersonTravel AgentAirlineHotelreservereservepayreserveCheck intravelpaypayreservepaytravelCheck inObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 306What Really is an Object?Reservation -- a promise to giveservice to a customerTicket -- record that customer haspaid for service in advanceFlightPayment -- an event (transaction?) inwhich money is exchanged8Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 307In fact, anything we can talk about can bean object, including associations ("thehusband of the first party", "first-bornson").The important question is what we aretrying to model.Models should be as simple as possible,but no simpler.Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 308Why this is importantMany of the objects in a good designare NOT problem domain objects.They can represent operations,processes, states, constraints,relationships, ...9Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 309Design for ReusePurpose is to make a system flexible,extensible, and easily changed.Make things objects if they need to bechanged and manipulated.Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 310Design for ReuseGoal is to build an application just byusing preexisting objects.• Compose, don't program.Relationship between objects asimportant as class hierarchy.10Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 311To Be or Not To Be --- A ClassAnalysis model shouldn’t containimplementation-specific objects likequeues and lists.Classes should be• unique• relevant• specificObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 312To Be or Not To Be --- A ClassOperations should not be objects unlessyou need to manipulate them.• A Call in a telephone billing systemhas attributes such as date anddestination phone number, and mustbe stored so it can be printed on themonthly bill.11Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 313The name of a class should represent itsintrinsic nature and not a role that itplays in an association.• A person can have many roles whenassociated with a car: owner,passenger, driver, lesee.Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 314What is an OO Model?A OO model is a model expressed in terms ofobjects, classes, and the relationshipsbetween them.Models can be written in programminglanguages, graphics, or English.12Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 315OMTgraphical OO modeling notation with threeparts• object model• dynamic model (event trace/statemachines)• functional model (data flow diagram)Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 316Object ModelObject, classes,attributes,operations, associations,inheritanceMammalPersonagebuy, sell,feedDogloudness, pricebarkownerpet13Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 317Multiplicity of Associations• exactly one• zero or more• zero or one• one or more• otherClassClassClass1+1-2, 4Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 318Dynamic ModelRecord order of events, dynamic interaction between objects.DogPersonDoorEvent TraceState Machinebarkopennotifygo thru doornotifycloseregisterregisterNeed to Leavedo: register with doordo: bark at personLeavingdo: unregisterdo: go through doordo: notify dependentsunregisternotify14Object-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 319Design vs. AnalysisUse of objects integrates design andanalysis.• advantages - easier to move fromone to the other• disadvantages - harder to tell whichyou are doingObject-oriented Programming and Design - Copyright 1998 by Ralph E. Johnson 320Analysis vs. DesignAnalysis produces documents thatcustomer can understand.Design produces documents thatprogrammers can