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2.1.Analysis

Requirementsanalysis 

sometimesrequiresindividuals/teamsfromclientaswellasserviceprovidersidestogetdetailedandaccuraterequirements;

oftentherehastobealotofcommunicationtoandfromtounderstandtheserequirements.Requirementgatheringisthemostcrucialaspectasmanytimescommunicationgapsariseinthisphaseandthisleadstovalidationerrorsandbugsinthesoftwareprogram.

2.2.Design

Thedesignstagetakesasitsinitialinputtherequirementsidentifiedintheapprovedrequirementsdocument.Foreachrequirement,asetofoneormoredesignelementswillbeproducedasaresultofinterviews,workshops,and/orprototypeefforts.

Designdescribesdesiredfeaturesandoperationsindetail,includingscreenlayouts,businessrules,processdiagrams,pseudocodeandotherdocumentation.

2.3.Development

Therealcodeiswrittenhere.

2.4.Testing

Thecodeistestedatvariouslevelsin 

softwaretesting.Unit,systemanduseracceptancetestingsareoftenperformed.Thisisagreyareaasmanydifferentopinionsexistastowhatthestagesoftestingareandhowmuchifanyiterationoccurs.Iterationisnotgenerallypartofthewaterfallmodel,butusuallysomeoccuratthisstage. 

2.5.Deployment

Thefinalstageofinitialdevelopment,wherethesoftwareisputintoproductionandrunsactualbusiness.

2.6.Maintenance

Whathappensduringtherestofthesoftware'

slife:

changes,correction,additions,andmovestoadifferentcomputingplatformandmore.This,theleastglamorousandperhapsmostimportantstepofall,goesonseeminglyforever.

3.MethodologiesandModels

Insoftwareengineering,therearesomemethodologiesandmodels.

ThemethodologiescontainsDevelopment（SSAD&

OOAD）、Maintenance，DataWarehousing、eLearning、ProductDevelopment.AndthemodelscontainsWaterfall、V-Model、RADModel、PrototypeModel、IncrementalModel、IterativeModel.

4.ProjectLifeCycle

Thecommonprojectlifecyclewilllikeflowbelow:

5.UML

UnifiedModelingLanguage 

（UML）isastandardizedgeneral-purpose 

modelinglanguage 

inthefieldof 

object-oriented 

softwareengineering.Thestandardismanaged,andwascreatedby,theObjectManagementGroup.

UMLincludesasetofgraphicnotationtechniquestocreate 

visualmodels 

of 

software-intensivesystems.

TheUMLcombinesthebestofthebestfrom:

✧DataModelingconcepts（EntityRelationshipDiagrams）

✧BusinessModeling（workflow）

✧ObjectModeling

✧ComponentModeling

5.1.UsageofUML

WecanuseUMLto

✧Displaytheboundaryofasystemanditsmajorfunctionsusingusecasesandactors

✧Illustrateusecaserealizationswithinteractiondiagrams

✧Representastaticstructureofasystemusingclassdiagrams

✧Modelthebehaviorofobjectswithstatetransitiondiagrams

✧Revealthephysicalimplementationarchitecturewithcomponent&

deploymentdiagrams

5.2.UseCaseDiagrams

Ausecaseisasetofscenariosthatdescribinganinteractionbetweenauserandasystem. 

Ausecasediagramdisplaystherelationshipamongactorsandusecases. 

Thetwomaincomponentsofausecasediagramareusecasesandactors.

Anactorisrepresentsauseroranothersystemthatwillinteractwiththesystemyouaremodeling. 

Ausecaseisanexternalviewofthesystemthatrepresentssomeactiontheusermightperforminordertocompleteatask.

Usecasesareusedinalmosteveryproject. 

Theyarehelpfulinexposingrequirementsandplanningtheproject.Duringtheinitialstageofaprojectmostusecasesshouldbedefined,butastheprojectcontinuesmoremightbecomevisible. 

5.3.SequenceDiagrams

Asequencediagramisaninteractiondiagramthatfocusesonthetime-orderingofmessages.Itrepresentstheinteractionbetweendifferentobjectsinthesystem.

Sequencediagramsdemonstratethebehaviorofobjectsinausecasebydescribingtheobjectsandthemessagestheypass. 

thediagramsarereadlefttorightanddescending. 

Theexamplebelowshowsanobjectofclass1startthebehaviorbysendingamessagetoanobjectofclass2. 

Messagespassbetweenthedifferentobjectsuntiltheobjectofclass1receivesthefinalmessage.

5.4.ClassDiagrams

Classdiagramsarewidelyusedtodescribethetypesofobjectsinasystemandtheirrelationships.Classdiagramsmodelclassstructureandcontentsusingdesignelementssuchasclasses,packagesandobjects.Classdiagramsdescribethreedifferentperspectiveswhendesigningasystem,conceptual,specification,andimplementation.Theseperspectivesbecomeevidentasthediagramiscreatedandhelpsolidifythedesign.ThisexampleisonlymeantasanintroductiontotheUMLandclassdiagrams.IfyouwouldliketolearnmoreseetheResourcespageformoredetailedresourcesonUML.

Classesarecomposedofthreethings:

aname,attributes,andoperations. 

Belowisanexampleofaclass:

Classdiagramsalsodisplayrelationshipssuchascontainment,inheritance,associationsandothers. 

Belowisanexampleofanassociativerelationship:

TheclassOrderisassociatedwiththeclassCustomer. 

Themultiplicityoftheassociationdenotesthenumberofobjectsthatcanparticipateintherelationship.1 

Forexample,anOrderobjectcanbeassociatedtoonlyonecustomer,butacustomercanbeassociatedtomanyorders.

Anothercommonrelationshipinclassdiagramsisageneralization. 

Ageneralizationisusedwhentwoclassesaresimilar,buthavesomedifferences. 

Lookatthegeneralizationbelow:

InthisexampletheclassesCorporateCustomerandPersonalCustomerhavesomesimilaritiessuchasnameandaddress,buteachclasshassomeofitsownattributesandoperations. 

TheclassCustomerisageneralformofboththeCorporateCustomerandPersonalCustomerclasses.ThisallowsthedesignerstojustusetheCustomerclassformodulesanddonotrequirein-depthrepresentationofeachtypeofcustomer. 

Nowgivethewholeclassdiagramofthisexample:

5.5.StateDiagrams

Statediagramsareusedtodescribethebehaviorofasystem. 

Statediagramsdescribeallofthepossiblestatesofanobjectaseventsoccur. 

Eachdiagramusuallyrepresentsobjectsofasingleclassandtrackthedifferentstatesofitsobjectsthroughthesystem. 

BelowisanexampleofastatediagrammightlooklikeforanOrderobject. 

WhentheobjectenterstheCheckingstateitperformstheactivity"

checkitems."

Aftertheactivityiscompletedtheobjecttransitionstothenextstatebasedontheconditions[allitemsavailable]or[anitemisnotavailable]. 

Ifanitemisnotavailabletheorderiscanceled. 

Ifallitemsareavailablethentheorderisdispatched. 

WhentheobjecttransitionstotheDispatchingstatetheactivity"

initiatedelivery"

isperformed. 

AfterthisactivityiscompletetheobjecttransitionsagaintotheDeliveredstate.

5.6.ActivityDiagram

Activitydiagramsdescribetheworkflowbehaviorofasystem. 

Activitydiagramsaresimilarto 

statediagrams 

becauseactivitiesarethestateofdoingsomething. 

Thediagramsdescribethestateofactivitiesbyshowingthesequenceofactivitiesperformed. 

Activitydiagramscanshowactivitiesthatareconditionalorparallel.

Belowisapossibleactivitydiagramforprocessinganorder. 

Thediagramshowstheflowofactionsinthesystem'

sworkflow. 

Oncetheorderisreceivedtheactivitiessplitintotwoparallelsetsofactivities. 

Onesidefillsandsendstheorderwhiletheotherhandlesthebilling. 

OntheFillOrderside,themethodofdeliveryisdecidedconditionally. 

DependingontheconditioneithertheOvernightDeliveryactivityortheRegularDeliveryactivityisperformed. 

Finallytheparallelactivitiescombinetoclosetheorder. 

5.7.PhysicalDiagrams

Therearetwotypesofphysicaldiagrams:

deploymentdiagramsandcomponentdiagrams.Deploymentdiagramsshowthephysicalrelationshipbetweenhardwareandsoftwareinasystem.Componentdiagramsshowthesoftwarecomponentsofasystemandhowtheyarerelatedtoeachother.Theserelationshipsarecalleddependencies.

Thecombineddeploymentandcomponentdiagramabovegivesahighlevelphysicaldescriptionofthecompletedsystem. 

ThediagramshowstwonodeswhichrepresenttwomachinescommunicatingthroughTCP/IP. 

Component2isdependentoncomponent1,sochangestocomponent2couldaffectcomponent1.Thediagramalsodepictscomponent3interfacingwithcomponent1. 

Thisdiagramgivesthereaderaquickoverallviewoftheentiresystem. 

6.Exercise

InordertomasterUMLbetter,Itakeanexampleforexercise.HereisacaseaboutHomeLoan.TheHomeLoanCustomerentersallthenecessarydetailsintheformtoapplyforaloanwiththesystem.

6.1.E-RDiagram

Insoftwareengineering,anentity-relationshipmodelisanabstractandconceptualrepresentationofdata.Entity-relationshipmodelingisadatabasemodelingmethod,usedtoproduceatypeofconceptualschemaorsemanticdatamodelofasystem,oftenarelationaldatabase,anditsrequirementsinatop-downfashion.Diagramscreatedbythispro