Unit-1 OOMD- Inthhro- class modeling.ppt

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1. Faculty Instructor:
Dr. kavitha sooda
Associate Professor
Dept. of CSE
B.M.S. College of engineering, Bengaluru
TB: Object oriented modelling and design with UML, 2
nd
Edition, Michael blaha, james Rumbaugh
©-PPT
Object-Oriented Modeling and Design
Course Code: 20cs6pcomd

2. Course Content
Units Content
1-C1,2,3 Introduction, Modeling Concepts, Class Modeling
2 –C4,5 Advanced Class Modeling, State Modeling
3 –C6,7,8 Advanced State Modeling, Interaction Modeling:
Advanced State Modeling
4 –C10-13 Process Overview, System Conception, Domain
Analysis, Application Analysis: Process Overview
5 -C14,15,17 System Design, Class Design, Implementation
Modeling
Unit-12

3. Course Outcomes
CO Course outcomes
CO1Ability to apply the knowledge of class, State & Interaction
Modelling using Unified Modeling Language to solve a
given problem.
CO2Ability to analyze a System for a given requirement using
Unified Modeling language
CO3Ability to design a given system using high level strategy.
CO4Ability to conduct practical experiment to solve a given
problem using Unified Modeling language.
Unit-13

4. Is Software Engineering the right
term?
If Engineering then it has to be constructed like Civil engineering, Electrical or
Mechanical Engineering
Unit-14

5. What is Software Development &
Engineering?
Software development is art of problem solving-
Just 100 years old
Software Engineering is an innovative process
Unit-15

6. Unit-1
6

7. Why projects Fail? -Complexity
Changes from requirements
Changes from Technology
Changes from People
Why Project fails?
Unit-17

8. Software Development life cycle
Unit-18

9. Software Development-Software
Construction
OOAD aids in
Structural analysis, Modeling, Design and
Implementation
Adherence to Good Practices.
UML
Unit-19

10. End of Class
Next Class,
Introduction, 4 Aspects of OO approach, OO
Development, Methodology, Themes
Unit-110

11. Content
Introduction
Four Aspects of OO Approach
OO Development
OO Themes
Unit-111

12. Introduction
IntentionofOOMDistolearnhowtoapplyobject-
orientedconceptstoallthestagesofthesoftware
developmentlifecycle.
Object-orientedmodellinganddesignisawayof
thinkingaboutproblemsusingmodelsorganizedaround
realworldconcepts.
Thefundamentalconstructistheobject,whichcombines
bothdatastructureandbehaviour.
Unit-112

13. Four Aspects of OO Approach
OOmeansthatweorganizesoftwareasacollectionof
discreteobjects.
TherearefouraspectsrequiredbyanOOapproach
Identity.
Classification.
Inheritance.
Polymorphism.
Unit-113

14. Identity:
Identitymeansthatdataisquantizedintodiscrete,
distinguishableentitiescalledobjects.
E.g.Personalcomputer,bicycle,queeninchess.
Objectscanbeconcreteorconceptual.Eachobject
hasitsowninherentidentity.
Classification:
Classificationmeansthatobjectswiththesame
datastructureandbehaviouraregroupedintoa
class.
E.g.paragraph,monitor,chesspiece.
Eachobjectissaidtobeaninstanceofitsclass.
Unit-114

15. Unit-115

16. Inheritance:
Itisthesharingofattributesandoperationsamong
classesbasedonahierarchicalrelationship.Asuperclass
hasgeneralinformationthatsubclassesrefineand
elaborate.
E.g.RegularCustomerandPrivilegedcustomerarethe
subclassesofCustomer.
Polymorphism:
Polymorphismmeansthatthesameoperationmaybehave
differentlyfordifferentclasses.
For E.g. move operation behaves differently for a pawn
than for the queen in a chess game.
Anoperationisaprocedure/transformationthatanobject
performsorissubjectedto.Animplementationofan
operationbyaspecificclassiscalledamethod.
Unit-116

17. OO Development
Unit-117

18. Developmentreferstothesoftwarelifecycle:Analysis,
DesignandImplementation.
TheessenceofOODevelopmentistheidentificationand
organizationofapplicationconcepts.
OOdevelopmentisfundamentallyawayofthinkingand
notaprogrammingtechnique
Unit-118

19. OO Methodology
Theprocessconsistsofbuildingamodelofan
applicationandthenaddingdetailstoitduringdesign.
Themethodologyhasthefollowing5stages:
Systemconception:Softwaredevelopmentbegins
withbusinessanalysisorusersconceivingan
applicationandformulatingtentativerequirements.
Analysis:Theanalystscrutinizesandrigorously
restatestherequirementsfromthesystemconception
byconstructingmodels.
Unit-119

20. Theanalysismodelisaconcise,preciseabstractionofwhat
thedesiredsystemmustdo,nothowitwillbedone.
Theanalysismodelhastwoparts:
DomainModel-adescriptionofrealworldobjects
reflectedwithinthesystem.
ApplicationModel-adescriptionofpartsofthe
applicationsystemitselfthatarevisibletotheuser.
E.g.Incaseofstockbrokerapplication-
Domainobjectsmayinclude-stock,bond,trade&
commission.
Applicationobjectsmightcontroltheexecutionoftrades
andpresenttheresults.
Unit-120

21. SystemDesign:Thedevelopmentteamsdeviseahigh-
levelstrategy-TheSystemArchitecture-forsolvingthe
applicationproblem.
Thesystemdesignershoulddecidewhatperformance
characteristicstooptimize,choseastrategyofattacking
theproblem,andmaketentativeresourceallocations.
ClassDesign:Theclassdesigneraddsdetailstothe
analysismodelinaccordancewiththesystemdesign
strategy.
Implementation:Implementerstranslatetheclassesand
relationshipsdevelopedduringclassdesignintoa
particularprogramminglanguage,databaseorhardware.
Unit-121

22. Three models
ClassModel—fortheobjectsinthesystem&their
relationships.
Itdescribesthestaticstructureoftheobjectsinthesystemand
theirrelationships.
Classmodelcontainsclassdiagrams-agraphwhosenodesare
classesandarcsarerelationshipsamongtheclasses.
Statemodel—forthelifehistoryofobjects.
Itdescribestheaspectsofanobjectthatchangeovertime.
Itspecifiesandimplementscontrolwithstatediagrams-a
graphwhosenodesarestatesandwhosearcsaretransition
betweenstatescausedbyevents.
Unit-122

23. InteractionModel—fortheinteractionamong
objects.
Itdescribeshowtheobjectsinthesystemco-operateto
achievebroaderresults.
Thismodelstartswithusecasesthatarethenelaborated
withsequenceandactivitydiagrams.
Usecase–focusesonfunctionalityofasystem–i.e
whatasystemdoesforusers.
Sequencediagrams–showstheobjectthatinteractand
thetimesequenceoftheirinteractions.
Activitydiagrams–elaboratesimportantprocessing
steps.
Unit-123

24. OO THEMES -6
Abstraction
Abstractionletsyoufocusonessentialaspectsofan
applicationwhileignoringdetailsi.efocusingonwhatan
objectisanddoes,beforedecidinghowtoimplementit.
It’sthemostimportantskillrequiredforOOdevelopment.
Encapsulation(informationhiding)
Itseparatestheexternalaspectsofanobjectfromthe
internalimplementationdetails.
Encapsulationpreventsportionsofaprogramfrom
becomingsointerdependentthatasmallchangehas
massiverippleeffects.
Unit-124

25. Combiningdataandbehavior
Callerofanoperationneednotconsiderhowmany
implementationsexist.
InOOsystemthedatastructurehierarchymatches
theoperationinheritancehierarchy.
Unit-125

26. Sharing
OOtechniquesprovidesharingatdifferentlevels.
Inheritanceofbothdatastructureandbehaviorletssub
classessharecommoncode.
OOofferstheprospectofreusingdesignsandcodeon
futureprojects.
Emphasisontheessenceofanobject
OOdevelopmentplacesagreateremphasisondata
structureandalesseremphasisonprocedurestructure
thanfunctional-decompositionmethodologies.
Synergy
Identity,classification,polymorphismandinheritance
characterizeOOlanguages.
Eachoftheseconceptscanbeusedinisolation,but
togethertheycomplementeachothersynergistically.
Unit-126

27. End of Chapter 1

29. Purpose of Modeling
Abstraction
Three models
Unit-1 29

30. Amodelisanabstractionofsomethingforthe
purposeofunderstandingitbeforebuildingit.
MODELLING
Designersbuildmanykindsofmodelsforvarious
purposesbeforeconstructingthings.
Modelsserveseveralpurposes–
Testingaphysicalentitybeforebuildingit:
MedievalbuiltscalemodelsofGothicCathedralsto
testtheforcesonthestructures.Engineerstestscale
modelsofairplanes,carsandboatstoimprovetheir
dynamics.
Unit-1 30

31. Communicationwithcustomers:Architectsandproduct
designersbuildmodelstoshowtheircustomers.
mock-upsaredemonstrationproductsthatimitatesomeof
theexternalbehaviourofasystem.
Visualization:Storyboardsofmovies,TVshowsand
advertisementsletwritersseehowtheirideasflow.
Artistssketchesletthemblockouttheirideasandmake
changesbeforecommittingthemtosoilorstone.
Reductionofcomplexity:Modelsreducecomplexityto
understanddirectlybyseparatingoutasmallnumberof
importantthingstodowithatatime.
Unit-1 31

32. Abstractionistheselectiveexaminationofcertain
aspectsofaproblem.
Thegoalofabstractionistoisolatethoseaspectsthat
areimportantforsomepurposeandsuppressthose
aspectsthatareunimportant.
Allabstractionsareincompleteandinaccurate.
Agoodmodelcapturesthecrucialaspectsofaproblem
andomitsothers.
Unit-1 32

33. ClassModel:representsthestatic,structural,“data”
aspectsofasystem.
Itdescribesthestructureofobjectsinasystem-their
identity,theirrelationshipstootherobjects,their
attributes,andtheiroperations.
Goalinconstructingclassmodelistocapturethose
conceptsfromtherealworldthatareimportanttoan
application.
Classdiagramsexpresstheclassmodel.
Unit-1 33

34. StateModel:representsthetemporal,behavioural,
“control”aspectsofasystem.
Statemodeldescribesthoseaspectsofobjects
concernedwithtimeandthesequencingof
operations–
Eventsthatmarkchanges,statesthatdefinethecontext
forevents,andtheorganizationofeventsandstates.
Statediagramexpressthestatemodel.
Eachstatediagramshowsthestateandevent
sequencespermittedinasystemforoneclassof
objects.
Statediagramrefertotheothermodels.
Unit-1 34

35. Interactionmodel–representsthecollaborationof
individualobjects,the“interaction”aspectsofa
system.
Interactionmodeldescribesinteractionsbetween
objects–howindividualobjectscollaboratetoachieve
thebehaviourofthesystemasawhole.
Usecases-documentinteractionbetweensystemand
actor.
Sequencediagrams-objectsthatinteractandtime
sequence.
Activitydiagrams–flowofcontrol.
Unit-1 35

36. RelationshipAmongtheModels
Theclassmodeldescribesdatastructureonwhichthe
stateandinteractionmodelsoperate.
Theoperationsintheclassmodelcorrespondtoevents
andactions.
Thestatemodeldescribesthecontrolstructureof
objects.
Theinteractionmodelfocusesontheexchanges
betweenobjects.
Thegoalistosimplifythesystemdescriptionwithout
loadingdownthemodelwithsomanyconstructsthat
itbecomesaburdenandnothelp.
Unit-1 36

37. Next Chapter : Class Modeling

38. CHAPTER 3

39. A class model captures the static structure of a system by
characterizing the objects in the system, the relationships
between the objects, and the attributes and operations for
each class of objects.
Object-generally Proper noun
Purpose of class modeling is to describe objects.
An object is a concept, abstraction or thing with identity
that has meaning for an application.
Ex: Joe Smith, Infosys Company, process number 7648
and top window are objects.
Unit-1 39

40. Someobjectsarereal-worldentities,conceptualetc.,
Thechoiceofobjectdependsonjudgmentandthenatureof
aproblem.
Allobjectshaveidentityandaredistinguishable.
Thetermidentitymeansthattheobjectsaredistinguished
bytheirinherentexistenceandnotbydescriptiveproperties
thattheymayhave.
Example:Twoappleswiththesamecolor,shapeand
texturearestillindividuals.
Identicaltwinsaretwodistinctpersonseventhoughthey
lookthesame
Unit-1 40

41. Class–CommonNoun
Anobjectisaninstanceoroccurrenceofaclass.
Aclassdescribesagroupofobjectswiththesame
properties(attributes),behaviour(operations),kinds
ofrelationshipsandsemantics.
Ex:Person,company,processandwindoware
classes.
Objectsinaclasshavethesameattributesandforms
ofbehavior.
Theobjectsinaclassshareacommonsemantic
purpose.
Unit-1 41

42. A barn and horse may have cost and age .
If considered as financial assets they both
could belong to same class.
If developer takes into consideration that a
person paints a barn and feeds a horse, they
would be modeled as distinct classes.
The interpretation of semantics depends on
the purpose of each application and is a
matter of judgment
Unit-1 42

43. ClassDiagrams
Classdiagramsprovideagraphicnotationformodeling
classesandtheirrelationships,therebydescribing
possibleobjects.
Classdiagramsareusefulbothforabstractmodelingand
fordesigningactualprograms.
Aclassdiagramcorrespondstoinfinitesetofobject
diagrams.
Anobjectdiagramshowsindividualobjectsandtheir
relationships.
Usefulfordocumentingtestcasesanddiscussing
examples.
Unit-1 43

44. Conventionsused(UML):
UMLsymbolforbothclassesandobjectsisbox.
Objectsaremodelledusingboxwithobjectname
followedbycolonfollowedbyclassname.
Useboldfacetolistclassname,centrethenameinthe
boxandcapitalizethefirstletter.Usesingularnounsfor
namesofclasses.
Toruntogethermultiwordnames(suchasJoeSmith),
separatethewordswithinterveningcapitalletter.
Unit-1 44

45. ValuesandAttributes
Valueisapieceofdata.
Attributeisanamedpropertyofaclassthatdescribesa
valueheldbyeachobjectoftheclass.
Objectistoclassasvalueistoattribute.
E.g.Attributes:Name,bdate,weight.
Values:JoeSmith,21October1983,64
Color,modelyearandweightareattributesofCarobjects.
Eachattributehasavalueforeachobject.
Differentobjectsmayhavethesameordifferentvaluesfor
agivenattribute.
Eachattributenameisuniquewithinaclass.
Unit-1 45

46. Conventionsused(UML):
•Listattributesinthe2ndcompartmentoftheclassbox.Optional
details(likedefaultvalue)mayfolloweachattribute.
•Acolonprecedesthetype,anequalsignprecedesdefaultvalue.
•Showattributenameinregularface,leftalignthenameinthe
boxandusesmallcaseforthefirstletter.
•Similarlywemayalsoincludeattributevaluesinthe2nd
compartmentofobjectboxeswithsameconventions.
Unit-1 46

47. Operations and Methods
Anoperationisafunctionorprocedurethatmaybeapplied
toorbyobjectsinaclass.
E.g.Hire,fireandpaydividendareoperationsonclass
Company.
Objectidentifiersnottobelistedintheclass,theyare
implicitinmodels
Open,close,hideandredisplayareoperationsonclass
Window.
Donotlistobjectidentifiers;theyareimplicitin
models.
Unit-1 47

48. Sameoperationmayapplytomanydifferentclasses.
Suchanoperationispolymorphic.
Amethodistheimplementationofanoperationfora
class.
E.g.Inclassfile,printisanoperationyoucould
implementdifferentmethodstoprintASCIIfiles,print
binaryfiles,printdigitizedpicturefiles.
Whenanoperationhasmethodsonseveralclasses,itis
importantthatthemethodsallhavethesamesignature.
Ex:printshouldnothavefilenameasanargumentfor
onemethodandfilepointerasanargumentfortheother
method.
Unit-1 48

49. Featureisagenericwordforeitheranattributeoroperations.
UMLconventionsused–
Listoperationsin3rdcompartmentofclassbox.
Listoperationnameinregularface,leftalignanduselowercaseforfirst
letter.
Optionaldetailslikeargumentlistandreturntypemayfolloweachoperation
name.
Parenthesisencloseanargumentlist,commasseparatethearguments.Acolon
precedestheresulttype.
Directions:in,out,inout(Tomodify)
Unit-1 49

50. Summary of Notation for classes
Unit-1 50

51. Alinkisaphysicalorconceptualconnectionamong
objects.
E.g.JoeSmithWorksForSimplexCompany.
Mathematically,wedefinealinkasatuple–thatis,alistof
objects.
Alinkisaninstanceofanassociationgenerallyappears
asVerb.
Anassociationisadescriptionofagroupoflinkswith
commonstructureandcommonsemantics.
E.g.apersonWorksForacompany.
Anassociationdescribesasetofpotentiallinksinthesame
waythataclassdescribesasetofpotentialobjects.
Unit-1 51

52. Unit-1 52

53. Conventionsused(UML):
Linkisalinebetweenobjects;alinemayconsistofseveral
linesegments.
Ifthelinkhasthename,itisunderlined.
Associationconnectsrelatedclassesandisalsodenotedby
aline.
Showlinkandassociationnamesinitalics.
Associationnameisoptional,ifthemodelisunambiguous.
Ambiguityariseswhenamodelhasmultipleassociations
amongsameclasses.
Associationsareinherentlybidirectional.
ForExample:WorksForconnectsapersontoacompany.
Employsconnectsacompanytoaperson
Unit-1 53

54. Developersoftenimplementassociationsin
programminglanguagesasreferencesfromoneobject
toanother.
Areferenceisanattributeinoneobjectthatrefersto
anotherobject.
ForExample:adatastructureforPersonmightcontain
anattributeemployerthatreferstoaCompanyobject,
andaCompanyobjectmightcontainanattribute
employeesthatreferstoasetofPersonobjects.
Unit-1 54

55. Multiplicity
Multiplicityspecifiesthenumberofinstancesofoneclass
thatmayrelatetoasingleinstanceofanassociatedclass.
Multiplicityconstrainsthenumberofrelatedobjects.
UMLconventions:
UMLdiagramsexplicitlylistsmultiplicityattheendsof
associationlines.
UMLspecifiesmultiplicitywithaninterval,suchas
◦“1”(exactlyone).
◦“1..”(oneormore).
◦“3..5”(threetofive,inclusive).
◦“*”(many,i.ezeroormore).
Unit-1 55

56. One-to One Multiplicity
Unit-1 56

57. Zero-to-One Multiplicity
Workstation may have one of its windows
designated as the console to receive general
error messages.
Unit-1 57

58. Unit-1 58

59. One can use the symbol “arrow( )” to make the
direction of the name clear.
Unit-1 59

60. Association end names
Multiplicityimplicitlyreferstotheendsof
associations.ForE.g.Aone-to-manyassociationhas
twoends–
◦anendwithamultiplicityof“one”
◦anendwithamultiplicityof“many”
Youcannotonlyassignamultiplicitytoan
associationend,butyoucangiveitanameaswell.
Unit-1 60

61. Apersonisanemployeewithrespecttocompany.
Acompanyisanemployerwithrespecttoaperson.
Associationendnamesareoptional.
Associationendnamesarenecessaryforassociationsbetween
twoobjectsofthesameclass.Theycanalsodistinguish
multipleassociationsbetweenapairofclasses.
Unit-1 61

62. Associationendnamesarenecessaryforassociationsbetween
twoobjectsofthesameclass.
Containerandcontentsdistinguishthetwousagesof
Directoryintheself-association.
Eachdirectoryhasexactlyoneuserwhoisanownerandmany
userswhoareauthorizedtousethedirectory.
Unit-1 62

63. Associationendnamesunifymultiplereferencestothe
sameclass.
Whenconstructingclassdiagramsyoushouldproperly
useassociationendnamesandnotintroduceaseparate
classforeachreferenceasbelowfigshows.
Unit-1 63

64. Objectson“many”associationendhavenoexplicitorderandcanbe
consideredasasetbutsometimesobjectshaveanexplicitorder
Orderingisaninherentpartofassociation.Youcanindicateanorderedset
ofobjectsbywriting“{ordered}”nexttotheappropriateassociationend.
Workstationscreencontaininganumberofoverlappingwindows.
Eachwindowonascreenoccursatmostonceandhaveanexplicitorder
thatisonlythetopmostwindowisvisibleatanypointonthescreen
Orderingsometimesoccursfor“many”multiplicity.
Unit-1 64

65. Bags and Sequences
Normally,abinaryassociationhasatmostonelinkforapairof
objects.
Multiplelinksforapairofobjectsispermittedbyannotatingan
associationendwith{bag}or{sequence}
Abagisacollectionofelementswithduplicatesallowed.
Asequenceisanorderedcollectionofelementswithduplicates
allowed.
Itineraryisasequenceofairportsandthesameairportcanbe
visitedmorethanonce,soyoushoulduse{sequence}andnot
{ordered}.
{ordered}and{sequence}annotationsaresame,exceptthatthe
firstdisallowsduplicatesandtheotherallowsthem.
Unit-1 65

66. Association Classes-Adverbs
Anassociationclassisanassociationthatisalsoa
class.
Likethelinksofanassociation,theinstancesofan
associationclassderiveidentityfrominstancesofthe
constituentclasses.
Likeaclass,anassociationclasscanhaveattributes
andoperationsandparticipateinassociations.
accessPermissionisanattributeofAccessibleBy.
UMLnotationforassociationclassisaboxattachedto
theassociationbyadashedline.
Unit-1 66

67. Important in many-to-many associations.
Attributesforassociationclassunmistakablybelongto
thelinkandcannotbeascribedtoeitherobject.
accessPermissionisajointpropertyofFileanduser
cannotbeattachedtoeitherfileoruseralonewithout
losinginformation.
Unit-1 67

68. Figureshowsattributesfortwoone-to-many
relationships.
Eachpersonworkingforacompanyreceivesasalary
andhasjobtitle.
Thebossevaluatestheperformanceofeachworker.
Attributesmayalsooccurforone-to-oneassociations.
Unit-1 68

69. •Figureshowshowit’spossibletofoldattributesforone-to-one
andone-to-manyassociationsintotheclassoppositea“one”
end.
Unit-1 69

70. Anassociationclassparticipatinginanassociation.
Usersmaybeauthorizedonmanyworkstations.Each
authorizationcarriesapriorityandaccessprivileges.
Auserhasahomedirectoryforeachauthorized
workstation,butseveralworkstationsandusercan
sharethesamehomedirectory.
Unit-1 70

71. Theassociationclasshasonlyoneoccurrenceforeachpairing
ofPersonandCompany.
Incontrasttherecanbeanynumberofoccurrencesofa
PurchaseforeachPersonandCompany.Eachpurchaseis
distinctandhasitsownquantity,dateandcost.
Unit-1 71

72. Qualified Associations
AQualifiedAssociationisanassociationinwhichan
attributecalledthequalifierdisambiguatestheobjects
fora“many”associationends.
Itispossibletodefinequalifiersforone-to-manyand
many-to-manyassociations.
Aqualifierselectsamongthetargetobjects,reducing
theeffectivemultiplicityfrom“many”to“one”.
Unit-1 72

73. Abankservicesmultipleaccounts.Anaccountbelongsto
singlebank.
Withinthecontextofabank,theAccountNumberspecifies
auniqueaccount.Bankandaccountareclasses,and
AccountNumberisaqualifier.
Qualificationreduceseffectivemultiplicityofthis
associationfromone-to-manytoone-to-one.
qualificationincreasestheprecisionofamodel.
Unit-1 73

74. Thenotationofaqualifierisasmallboxontheend
oftheassociationlinenearthesourceclass.
Thequalifierboxmaygrowoutofanyside(top,
bottom,left,right)ofthesourceclass.
Thesourceclassplusthequalifieryieldsthetarget
class.
Bank+accountNumberyieldsanAccount,therefore
accountNumberislistedinaboxcontiguoustoBank.
Unit-1 74

75. Astockexchangelistsmanycompanies.However,it
listsonlyonecompanywithagiventickersymbol.
Acompanymaybelistedonmanystockexchanges,
possiblyunderdifferentsymbols.
Unit-1 75

76. Next Class :
Generalization, Example, OCL
Unit-1 76

77. Generalizationistherelationshipbetweenaclass(the
superclass)andoneormorevariationsoftheclass(the
subclasses).
Generalization(is-a)organizesclassesbytheirsimilarities
anddifferences,structuringthedescriptionofobjects.
Thesuperclassholdscommonattributes,operationsand
associations;thesubclassesaddspecificattributes,
operationsandassociations.
Eachsubclassissaidtoinheritthefeaturesofitssuperclass.
Unit-1 77

78. Unit-1 78

79. Generalizationistransitiveacrossanarbitrarynumberof
levels.
Thetermancestoranddescendentreferstogeneralization
ofclassesacrossmultiplelevels.
Aninstanceofasubclassissimultaneouslyaninstanceof
allitsancestorclasses.
Aninstanceincludesavalueforeveryattributeofevery
ancestorclass.
Aninstancecaninvokeanyoperationonanyancestorclass.
Eachsubclassnotonlyinheritsallthefeaturesofits
ancestorsbutaddsitsownspecificfeaturesaswell.
Ex:PumpaddsattributessuctionPressure,
dischargePressureandflowratewhichotherkindsof
equipmentdonotshare.
Unit-1 79

80. Unit-1 80

81. ‘move’,‘select’,‘rotate’,and‘display’areoperations
thatallsubclassesinherit.
‘scale’appliestoone-dimensionalandtwo-dimensional
figures.
‘fill’appliesonlytotwo-dimensionalfigures.
Ageneralizationsetnameisanenumeratedattribute
thatindicateswhichaspectofanobjectisbeing
abstractedbyaparticulargeneralization.
Thewordwrittennexttothegeneralizationline
diagram-dimensionality-isageneralizationsetname.
Unit-1 81

82. Therecanbemultiplelevelsofgeneralization.
Eachobjectinheritsfeaturesfromoneclassateach
levelofgeneralization.
UMLconventionused:
Uselargehollowarrowheadtodenotegeneralization.
Thearrowheadpointstosuperclass.
Unit-1 82

83. Useofgeneralization–3purposes
Tosupportpolymorphism:Youcancallanoperation
atthesuperclasslevel,andtheOOlanguagecomplier
automaticallyresolvesthecalltothemethodthat
matchesthecallingobject’sclass.
Tostructurethedescriptionofobjects:i.e.toforma
taxonomyandorganizingobjectsonthebasisoftheir
similaritiesanddifferences.
Toenablereuseofcode:Inheritcodefromthe
previousapplicationaswellasfrompreviouswork.
Reuseismoreproductivethanrepeatedlywritingcode
fromscratch.
Unit-1 83

84. Thetermsgeneralization,specializationandinheritance
allrefertoaspectsofthesameidea.
Generalizationderivesfromthefactthatthesuperclass
generalizesthesubclasses.
Specializationreferstothefactthatthesubclassrefine
orspecializethesuperclasses.
Inheritanceisthemechanismforsharingattributes,
operations,and associationsvia the
generalization/specializationrelationship.
Unit-1 84

85. Overridingfeatures
Asubclassmayoverrideasuperclassfeaturebydefininga
featurewiththesamename.Theoverridingfeature
(subclassfeature)refinesandreplacestheoverridden
feature(superclassfeature).
Whyoverridefeature?
Tospecifybehaviorthatdependsonsubclass.
Totightenthespecificationofafeature.
Toimproveperformance.
Intheexample:”Figure”eachleafsubclasseshad
overridden‘display’feature.
Youmayoverridemethodsanddefaultvaluesofattributes.
Youshouldneveroverridethesignature,orformofa
feature.
Unit-1 85

86. 3. 4 A Sample Class model
Unit-1 86

87. Unit-1 87

88. Unit-1 88

89. Expressing the behavior of navigating among classes.
Navigation is important because it lets you exercise a
model and uncover hidden flaws and omissions so that
you can repair them.
Example:
An institution may issue many credit card accounts, each
identified by an account number. Each account has a
maximum credit limit, a current balance, and a mailing
address. The account serves one or more customers
who reside at the mailing address. The institution
periodically issues a statement for each account. The
statement lists a payment due date, finance charge, and
minimum payment.
Unit-1 89

90. What transactions occurred for a credit card
account within a time interval?
What volume of transactions were handled by
an institution in the last year?
What customers patronized a merchant in the
last year by any kind of credit card?
How many credit card accounts does a
customer currently have?
What is the total maximum credit for a customer,
for all accounts?
Unit-1 90

91. Unit-1 91

92. Attributes. The syntax is the source object, followed by
a dot, and then the attribute name.
For example, the expression
aCreditCardAccount.maximumCredit takes a
CreditCardAccount object and finds the value of
maximumCredit.
Operations. An operation must be followed by
parentheses, even if it has no arguments
Simple associations. The target end may be indicated
by an association end name or, where there is no
ambiguity, a class name. In the example,
aCustomer.MailingAddress yields a set of addresses for
a customer.
Unit-1 92

93. Qualified associations. A qualifier lets you make a
more precise traversal. The expression
aCreditCardAccount.Statement[30 November 1999]
finds the statement for a credit card account with the
statement date of 30 November 1999.
Association classes. Given a link of an association
class, you can find the constituent objects. Alternatively,
given a constituent object, you can find the multiple links
of an association class.
Generalizations. Traversal of a generalization hierarchy
is implicit for the OCL notation.
Filters. There is often a need to filter the objects in a set.
The OCL has several kinds of filters, the most common
of which is the select operation.
Unit-1 93

94. Unit-1 94

95. What transactions occurred for a credit card account
within a time interval?
aCreditCardAccount.Statement.Transaction->
select(aStartDate <= transactionDate and
transactionDate <= anEndDate)
What volume of transactions were handled by an
institution in the last year?
anInstitution.CreditCardAccount.Statement.Transaction-
> select(aStartDate <= transactionDate and
transactionDate <= anEndDate).amount->sum()
What is the total maximum credit for a customer, for all
accounts?
aCustomer.MailingAddress.CreditCardAccount.
maximumCredit->sum()
Unit-1 95

96. End of Unit-1
Next Class –Advanced Class Modeling,
Chapter 4