eBook - The Practical Guide to Use Cases.pdf

The Practical Guide to Use Cases Learnusecasesviaprac-calexamples,-ps&templates

MichaelShrivathsan

Copyright©2012Accomp Copyright©2012Accompa,Inc.,SantaCla a,Inc.,SantaClara,California ra,California

www.accompa.com/use-case-book FirstEdition Allrightsreserved.Nopartofthisbookmaybereproducedinanyformorbyanyelectronicor Allrightsreserved.Nopartofthisbookmaybereproducedinanyform orbyanyelectronicor mechanicalmeans,includinginform mechanicalmeans,includinginformationstorageandretrievalsystem ationstorageandretrievalsystems,withoutpriorwritten s,withoutpriorwritten permissionfromAccompa,Inc.,exceptbyareviewerwh permissionfromAccompa,Inc.,exceptbyareviewerwhomayquoteabriefpassageas omayquoteabriefpassageas permittedunderSections107or108ofthe1976UnitedStatesCopyrightAct. Trademarkednamesappearinthisbook.Ratherthanuseatrademarksymbolwithevery occurrenceofaname,weusethenamessolelyinaneditorialfashionandtothebeneQitoft occurrenceofaname,weusethenamessolelyin aneditorialfashionandtothebeneQitoft he trademarkowner,withnointentionofinf trademarkowner,with nointentionofinfringement. ringement.

The Practical Guide to Use Cases

FormyGrandma,whotaughtme FormyGrandma,whotaughtmetoworkhard toworkhard anddreambig.

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FormyGrandma,whotaughtme FormyGrandma,whotaughtmetoworkhard toworkhard anddreambig.

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Table of Contents Preface ............................................................ ........................................................................................................................... .................................................................................. ...................4 1. Introduction ....................................................... ....................................................................................................................... ........................................................................ ........5 2. What’s in a Name? ....................................................... .................................................................................................................... .............................................................6 3. The Who ............................................................... ............................................................................................................................... ........................................................................ ........7

4. The Why ............................................................... ............................................................................................................................... ........................................................................ ........8

5. All the Jargon That’s Fit to Print! ................................................................ ..................................................................................... .....................10 6. How to Write a Use Case ............................................................ ...................................................................................................... ..........................................11 7. All the Jargon That’s Fit to Print – The Sequel .............................................................13 8.H 8.How owt to oWr Writ ite e“F “Ful ully ly-D -Dre ress ssed ed” ”Us Use eCa Case ses s(“ (“Na Nake ked” d”i is sso sooo oos sto tone nea age ge!) !) ...............14 9. Relationship Tips .............................................................. ................................................................................................................... .....................................................17

10. How to Write Use Cases for a Real-World Project ....................................................18 11. Templates and Tools ................................................................ .......................................................................................................... ..........................................22 12. Ten Do’s ......................................................... ......................................................................................................................... .......................................................................... ..........24 13. Frequently Asked Questions ............................................................ ............................................................................................ ................................26 14. Further Reading .............................................................. ................................................................................................................... .....................................................28 15. Glossary ......................................................... ......................................................................................................................... .......................................................................... ..........29 AboutAccompa-Softwar AboutAccompa-SoftwaretoManage etoManageUseCase UseCases s ............................................................31

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Preface Whoisthisbookfor? Ifyouparticipateinsoftwaredevelopmentprojects,thisbookcanhelpyou.The mostcommonjobrolesthatthisbookistargetedatinclude: • • • •

BusinessAnalysts Project/ProgramManagers Programmers Peopleinotherrelatedroles

• • •

ProductManagers EngineeringManagers ATesters

Whatisthegoalofthisbook? Mygoalforthisbookistohelpyoulearnthe practical f undamentalsof“Use Cases”foruseinsoftwaredevelopmentprojects. Ifyouareabeginnertothetopicof“UseCases”–thisbookcanhelpyoulearnthe basicsofthistopicandbuildastrongfoundation.Ifyouareanexperiencedveteran –thisbookcanhelpyoutrainothersaboutusecases.

HowamIqualifiedtowritethisbook? Igotstartedwritingsoftwarerequirementsinthemid-1990s.SincethenI’vebeen writingrequirements,managingteamswhowritethem,and/ortrainingteamsto writebetterrequirements–includingusecases.I’veperformedtheserolesfor5 successfulhigh-techcompaniesinSiliconValley. Since2009,I’vebeentheVPofProductManagementfor Accompa–wemakethe popularcloud-basedrequirementsmanagementsoftware.Inthisrole,I’veworked withanumberofourcustomers(Fortune-500companiestogrowingstartups)to helpthemimplementusecasesintotheirrequirementsmanagementprocess. IstartedwritingthisbooktohelpAccompacustomers.Idecidedtoshareitwith everyoneasIrealizedmorepeoplecouldbeneQitfromit.

Howisthisbookorganized? WestartwithasimpledeQinitionandanexample.WethenuseaQictionalproject (onlinebookstore)toQleshoutusecases.Alongtheway,we’lldeQineandexplain variousconceptsandterms.Youcanreadthisbookovermultiplesessions. Thisbookdoesnotcovercomplextheories.Instead,itfocusesonhowusecasescan helpyouinreal-lifeprojects.Justtheessentials,ma’am!

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1. Introduction Letusdiverightintoit.Whatexactlyisa“UseCase”anyhow? We’llstartwithasimpledeQinitionQirst.We’llthenreQineitafewtimesaswe progressthroughthebookandarriveatourQinaldeQinitioninalaterchapter.

“UseCase”Defini-on#1 Simplyput: A “Use Case” describes how a user reaches a specific goal.

Soundsverysimple-right?Well,notsofast!ThisisonlyapreliminarydeQinition, we’llmakeitmorecomplexsoon–Ipromise! We’lldeQinethetermsitalics(i.e.userand goal )laterinthisbook.Wewilleven deQineabettertermtouseinplaceofuser . Nowletustakealookatasampleusecase.

UseCaseExample#1 Throughoutthisbook,wewilluseaQictionalprojecttodemonstratethevarious conceptsaboutusecases.Thisprojectinvolvesbuildingan“OnlineBookstore”. Here‘sabasicexampleofausecaseforthisproject: Buyabook UserQindsabookhewantsandplacesanorder.Systemacceptstheorder,and sendsitforfulQillment. Asyoucanseefromthisexample,ausecasecanbeverysimple.Inthenextchapter, wewillclarifysometerminologymanypeopleQindconfusing.Thenwewilldive deeperintousecases. Beforewedothat,hereisafunexerciseforyou.

Exercises 1)

Writeabasicusecaseforyourproduct.Itdoesn’thavetobe“correct”-just writeitbasedontheexampleabove,youwillreviseitinlaterexercises.

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2. What’s in a Name? UseCasesvs.Requirements Aquestionthatcomesupoftenis“Areusecasesrequirements?” Fortunately,theanswerisprettysimple.Andtheansweris:“Yes”! Usecasesareindeedrequirements–infact,theyrepresentaspeciQictypeof requirementcalled“ Functional”Requirement . Usecasesareactuallyoneofthebestwaysofdocumentingthefunctional requirements(sometimesreferredtoasBehavioralRequirements)ofasystem. Pleasenotethatinadditiontousecases,othertypesofrequirements(suchasNonfunctional,UI,etc)arealsoneededtofullydocumenttherequirementsofaproject. UseCasesvs.UserStories(Agile) IfyouarepartofateamthatfollowsAgiledevelopmentprocess(suchasScrum,XP, etc),you’reprobablyfamiliarwithUserStories. Youmightbewonderingwhattheheckisthedifferencebetween UseCasesand User Stories.Hey,afteralltheybothstartwiththeletters“Use”-right? OneofthebestexplanationsofthisdifferencecomesfromAndrewStellmaninthis blogpost .Here’saquicksummary(Irecommendthatyoureadtheentireblogpost whenyouhavetime)… UserStoriesdescribe“userneeds”–i.e.somethingthattheuserneedstodoinhis day-to-dayjob. Userstoriesdon’tcontainalotofdetails,theyareusuallyjust1or2short sentences.Theyarenotrequirementsbythemselves,butrather “conversationstarters”or“pointers”torequirements. •

UseCases,ontheotherhand,describethebehavioryou’llbuildintothesystemto meetuserneeds. Usecasesdescribeacompleteinteractionbetweenthesystemand user .Asa result,usecasesarerequirementsbythemselves. •

Insummary-UseCasesandUserStoriesaredifferentthings. Thatsaid- I’veseen someteamscreate“lightweight”usecases(suchastheexampleinchapter1ofthis book)andusetheminagileorhybrid-agileprojectsinplaceofepicuserstories.This isacontroversialapproachthough,andisgenerallynotrecommended. Nowthatwe’veclariQiedtheseterms,letuslookatwhoreadsandwritesusecases.

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3. The Who Whoreadsusecases? Theprimaryreadersofusecasesare:Peoplewhoneedtounderstandwhatthe systembeingdevelopedmustdofunctionally.Thisincludesrolessuchas: Programmers Atesters Project/programmanagers,and Peopleinrelatedroles • • • •

Peoplewhoneedtoreview&approvethefunctionalityalsoreadusecases.This includesrolessuchas: Managers&Executives Customers Partners • • •

Whowritesusecases? Theprimarywritersofusecasesare:Peoplewhoneedtocommunicatetoothers whatthesystembeingdevelopedmustdofunctionally.Thisincludesrolessuchas: Productmanagers Businessanalysts Systemanalysts Project/programmanagers,and Peopleinrelatedroles • • • • •

Ok,nowthatwe’vedeQinedwhoreadsandwritesusecases-letusconsiderthe beneQitsofusingusecases.

Exercises 1) 2)

Writealistofpeopleinyourorganizationwhowillreadusecases. Writealistofpeopleinyourorganizationwhowillwritetheusecases.

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4. The Why BenefitsofUseCases DocumentingfunctionalrequirementsviaUseCasesofferskeybeneQitstoall stakeholders-asusecasesarewrittenusingastandardtemplateandprocess: Programmers: Usecasesareeasiertoreadandunderstand.Nolong-winded,unstructured textthatcausesreaderstosufferMEGO(MyEyesGlazeOver). Users,Customers: Usecasesareeasytoreviewandprovidefeedback. Approvers&Executives: Usecasesmakeiteasiertoidentifywhatneedstoberemoved,andwhatis missing. •

•

•

Inaddition,usecasesalsoformanexcellentframeworkfornon-functional requirementsofthesystem–suchasperformance,scalability,userinterface,etc. LetusnowlookatasimpleexamplethatdemonstratesthesebeneQits.

Example:UnstructuredText&Structured UseCase BAD–UnstructuredText: Buyingabook Onlinebookstorehasawebsitethatcanbeaccessedovertheinternet.Theonline bookstorewebsiteoffersalistofbooks.Thislistcanbesearchedbyusers.The websiteprocessesandshipsbooktoanyonewhobuysabookfromtheonline bookstore.

GOOD–Structured UseCase: Buyabook 1. Uservisitsonlinebookstorewebsite. 2. Bookstorewebsitedisplaysasearchbox. 3. Usersearchesforthebookheislookingfor:Usingauthor,ISBNand/ortitle. 4. Bookstorewebsitedisplaysalistofmatchingbooks. 5. Userplacestheorderforoneormorebooks. 6. BookstorewebsiteprocessestheorderanddisplaysconQirmationtouser.

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Asyoucansee,theusecasedescribesthefunctionalrequirementsofasysteminan easy-to-understand,structured textformat.Itismucheasiertoreadandunderstand comparedtotheunstructuredtext. Usecaseanswersquestionslikewho,whenand how muchmoreclearly. FYI:Inareal-worldproject,thisusecaseshouldbebrokeninto3or4separateuse cases.Wewilldojustthislateroninthisbook.I’vewrittenitasoneusecaseabove justtoquicklydemonstratetheadvantagesofusecasesoverabloboftext.

Nowwe’rereadytolookatamorecompletedeQinitionof“UseCase”.

Exercises 1) 2)

WritealistofbeneQitsyourorganizationcanenjoythroughusecases. ForeachbeneQit,identifywho(i.e.whichjobrole)willenjoythatbeneQit.

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5. All the Jargon That’s Fit to Print! “UseCase”Defini-on#2 Here’sabetterdeQinition: A “Use Case” describes how an actor interacts with a system in order to achieve a goal.

LetusnowdeQinethetermsinitalicsabove,aswellasafewotherkeyterms frequentlyusedwhendiscussingusecases.

Defini-onsofCommonTerms(Part1) System Acomputer,electronicormechanicalsystem(oracombinationthereof)that iscapableofinteraction. SystemUnderDesign(SUD) TheSystemwe’redevelopingintheprojectforwhichwe’rewritingtheuse case. ExternalSystem ASystemthatisoutsideoftheSUD. Actor AhumanpersonoranExternalSystem. Goal Theobjectivethe Actorhas.Thisiswhythe ActorinteractswiththeSUDin themannerdescribedinaspeciQicusecase. Pre-condition ThestatethattheSUDwasinbeforetheinteractionsdescribedintheuse casestart. Post-condition ThestatethattheSUDwillendupinaftertheinteractionsdescribedinthe usecasearecompleted.

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6. How to Write a Use Case RevisedExample Nowletusrevisetheusecasewewroteearliertomakeitmorethorough.

Buyabook,usingsearch SUD:OnlineBookstoreWebsite.Referredtoas“Bookstore”. Actor:Consumer

1. ConsumervisitsapageontheBookstoreusingawebbrowseronan internet-connectedcomputer. 2. Bookstoredisplaysthepage,whichincludesasearchbox. 3. Consumersearchesforthebookheislookingfor:Usingauthor,ISBNand/or title. 4. Bookstoredisplaysalistofmatchingbooks. 5. Consumeraddsoneormorebookstotheshoppingcart. 6. Consumerrepeatssteps3-5untilhehasaddedallthebookshewantsto purchasetotheshoppingcart. 7. Consumerinitiatescheckout. 8. Bookstorepromptsconsumertoenterorselectbilling&shippingaddresses. 9. Consumerentersaddresses. 10. Bookstorepromptsconsumertoenterorselectpaymentinformation. 11. Consumerenterspaymentinformationandplacesorder. 12. BookstoreprocessestheorderanddisplaysconQirmation&cross-sell informationtoconsumer.

5TipsforWri-ngaUseCase Hereare5tipsthatwillhelpyouinwritingusecases. 1. Startthetitleofeachusecasewithanactiveverb. o Noticehowinourexampleabove,westartedthetitlewiththeactive verb“Buy”. 2. Writeusingtheformatof: o ActordoesA o SystemdoesBinresponse o UserdoesC o SystemdoesDinresponse o … o Goalachieved

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3. Startwritingtheusecase.Evenifitisroughandmissingkeyparts,start writingitQirst.Thenyoucanreviseittoimproveitandaddfurtherdetails. 4. Rememberourendgoalinwritingusecases:Wewanttodocument functionalrequirementsinaneasy-to-understandformat.Aslongaswe achievethisgoal,itistotallyQineifourusecasedoesnotfollowtherigid structure&rulessometimesprescribedby“usecasepurists”. 5. Ifausecasegetstoolong(saywellmorethan10-15steps),consider breakingitdownintotwoormoreusecases.Thiswillkeepourusecases easytoread. o Differentusecasescanbeconnectedtogetherusingthetipsin “LinkingUseCases”laterinthisbook. NowletusimproveourdeQinitionof“UseCase”further,andarriveataQinal deQinition.

Exercises 1)

Revisetheusecaseyouwrotein exercise1.1-usingtheexampleandtipsin thissection.Youshouldendwithausecasethatlookssimilartotherevised exampleinthissection.

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7. All the Jargon That’s Fit to Print – The Sequel “UseCase”–FinalDefini-on Here’sourQinaldeQinitionof“usecase”: A “Use Case” describes the story of an actor interacting with the system under design (SUD) while achieving or failing to achieve a goal.

Thus,acompleteusecasedescribestheinteractionwhentheusersucceedsin achievingagoal,andwhenshefailstoachieveagoal.

Defini-onsofCommonTerms(Part2) PrimaryActor The Actor whoinitiatesaninteractionwiththeSUDtoachievetheGoal . Scenario Sequenceofinteractionsunderonecondition(suchas:UserQindsthebook he’slookingfor,UserisunabletoQindthebook,etc).Oneormorescenarios (makingupsuccess aswellas failureconditions)makeupausecase. MainSuccessScenario(MSS) TheScenarioinwhichnothinggoeswrong,andthePrimaryActor achieves theGoal . Extension AScenarioduringwhichsomethinggoeswrong,orsomethingdeviatesfrom theMSS . UseCaseID AuniqueID assignedtoausecase.WeshouldassignauniqueIDtoeachuse casewewrite–thismakesiteasiertocommunicateaboutalistofusecases.

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8. How to Write “Fully-Dressed” Use Cases (“Naked” is sooo stone age!) Example–Revised NowletusrevisetheusecasewewroteearliertoincludeExtensions.Wewillalso maketheusecasemore“fullydressed”(i.e.morestructured). Name:

Buyabook,usingsearch

SUD:

OnlineBookstoreWebsite.Referredtoas“Bookstore”.

ID:

UC-1

PrimaryActor:

Consumer

Pre-condition:

Consumerisonacomputerconnectedtotheinternet.

MainSuccess Scenario:

1. ConsumervisitsapageontheBookstoreusingaweb browseronaninternet-connectedcomputer. 2. Bookstoredisplaysthepage,whichincludesasearch box. 3. Consumersearchesforthebookheislookingfor:Using author,ISBNand/ortitle. 4. Bookstoredisplaysalistofmatchingbooks. 5. Consumeraddsoneormorebookstotheshopping cart. 6. Consumerrepeatssteps3-5untilhehasaddedallthe bookshewantstopurchasetotheshoppingcart. 7. Consumerinitiatescheckout. 8. Bookstorepromptsconsumertoenterorselectbilling &shippingaddresses. 9. Consumerentersaddresses. 10. Bookstorepromptsconsumertoenterorselect paymentinformation. 11. Consumerenterspaymentinformationandplaces order. 12. Bookstoreprocessestheorderanddisplays conQirmation&cross-sellinformationtoconsumer.

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Extensions: 4. (Extensionstosearch) A.Nomatchesfound i. Bookstoredoesnotfoundanymatches, andpromptstheconsumertorevisehis searchterms. ii. Consumerrevisessearchtermsand repeatsstep3ofMSS. B.Matchfound,butbookisoutofstock i. Bookstoreinformsconsumerthatthe bookisoutofstock,andisnotavailable forpurchase. ii. Consumeraddsthebooktohis“Alert List”,sothatBookstorecanemailhim onceitisavailable. 12. (Extensionstoorderprocessing) A.Paymentinformationisinvalid i. BookstoreQindsthepaymentinformation invalid,andpromptstheconsumertoreenterpaymentinformation. ii. Consumerre-enterspaymentinformation andrepeatsstep11ofMSS. Post-condition:

Consumerhassuccessfullyplacedtheorder.

Pleasenotethatinadditiontoaddingextensions,we’vealsoaddedmore “structureddata”tothisusecase.SpeciQically: ID Pre-condition Post-condition • • •

5TipsforWri-ngExtensions Hereare5tipsthatwillhelpyouwrite extensionsforausecase. 1. ForeverystepinMSSwherebehaviorcanbranchduetoa failurecondition– writedowntheconditionandthestepstohandleit. o Eachextensionisjustaveryshortusecasetohandlea failure condition. 2. Brainstormallpossible failureconditionswithyourteam.Thenprioritizethe extensionstodeterminewhichonesyouwillcoverinyourusecases. o Spendthetimetodothisstepwell. o Formostsoftwaresystems,documentingtheextensionscantakeas muchtime(ifnotmore)asdocumentingtheMSS.

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Missingextensionsareoneofthetopcausesofpoorlydesigned products. o Thatsaid–youmuststrikeabalancebetweenavailabletimeand documentingeveryconceivableextension.Documentingevery conceivableextensionisoftennotrealistic-aseachstepinan extensioncanhaveitsownfailurecondition,andsoforth. 3. Eachextensionshouldendbyeither: o Re-mergingwithMSSsuccessfully,or o Primaryactorabandoningthegoal. 4. Writeeachextensionusingtheformatof: o NumbertheparentbulletoftheextensionusingthestepoftheMSS (suchas“4”,“12”intheaboveexample)wherebehaviorbranchesdue to failurecondition. o Giveeach failureconditionauniquenumber(suchas“4.A”,“4.B”and “12.A”intheaboveexample). o Titletheextensionusingabriefdescriptionof failurecondition.See thelineswithboldfont intheaboveexample. o Foreachextension,listnumberedstepsthatdescribehowSUDwill handlethecondition. o Theformatdescribedabovecanbeeasilyachievedwithsoftwaresuch asMicrosoftWordorAccompa. 5. Ifanextensiongetsverycomplicated,convertthatextensionintoanew, separateusecase. o Youcanlinkthenew(extension)usecasetotheparentusecase (MSS)usingthetipsin“LinkingUseCases”sectionbelow. o

Exercises 1) 2)

Revisetheusecaseyouwrotein exercise6.1–tomakeitfully-dressedasin theexamplethissection.YoucandownloadtheWordtemplatefromhere. Write 2-3 extensionsforyourrevisedusecaseusingtheexampleandtipsin thissection.

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9. Relationship Tips LinkingUseCasesRela-onships Inreal-worldprojects,usecasesareoftenrelatedtooneanother.Itisvery beneQicial–andoftenabsolutelynecessary-tocreateanddocumentthese relationshipsaswewritealargenumberofusecases.Thiswillhelpusperform impactanalysisandtracingofourusecases. Thetwomostcommontypesofrelationshipsusedbetweenusecasesare“Extends” and“Includes”.Here’sadeQinitionoftheserelationships: Letusassumewehave3usecases: UC-1:Buyabook UC-5:Fixinvalidcreditcardinformation UC-14:Searchforabook • • •

Extends Wesay“UC-5extendsUC-1”whenUC-5describesan ExtensionofUC-1–i.e.a failureconditionforoneofthestepsintheMSSofUC-1. FYI:Thefollowingtwodescriptionsmeanthesamething: UC-5extendsUC-1 UC-1isextendedbyUC-5 • •

Includes Wesay“UC-1includesUC-14”whenUC-14describesastepofUC-1inmore detail. FYI:Thefollowingtwodescriptionsmeanthesamething: UC-1includesUC-14 UC-14isincludedbyUC-1 • •

WhileitispossibletocreateandmanagerelationshipsusingtoolssuchasMicrosoft Wordorwikis–mostteamsQinddedicatedrequirementsmanagementtoolssuchas Accompainvaluableforthispurpose.

Exercises 1) 2)

Identify1-2usecasesthat“extend”yourusecase.Youcansimplyconvertthe extensionsyouwroteinexercise8.2intoseparateusecases. Identify1-2usecasesthatare“includedby”yourusecase.

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10. How to Write Use Cases for a Real- World Project Herearethestepsforwritingusecasesforareal-worldproject. Tip:Meetwithyourteamtoperformsteps1-4togetherasateam.Youcanthen workonstep5.1byyourself.Thenyoucanmeetwithyourteamagaintoreview MSS,andidentifyallfailureconditions(i.e.step5.2).

1. Createalistofactors(people,externalsystems). 2. Createalistofgoalsforeachactor-i.e.whateachactorwantstoachieve usingyoursystem. 3. NowyouhavetheQirstdraftofyourlistofusecases!Eachgoalbecomesa usecase. 4. Prioritizetheusecasesinyourlist.Priorityshouldbeassignedbasedonthe businessimportanceof: Theactor,and Thegoal. 5. Fleshouteachusecase: 5.1. DeQinethesuccessconditionforeachusecaseindetail–i.e.Main SuccessScenario. 5.2. Meetwithyourteamtoidentifyfailureconditionsforeachusecase. Createextensionstoaddressallmajorfailureconditions. 5.3. ItistotallyQinetocoversomeextensions,atQirst,onlyatahigh-level. Lateron,youcanQleshthemoutinmoredetail–andevenconvert themintoseparateusecases. 5.4. Incompleteusecasesresultfrequentlyfromforgettingfailure conditions,andcanleadtoasub-optimaluserexperience.Makesureto identifyallthekeyfailureconditions. § §

SampleListofUseCasesforanOnlineBookstore Herearesomeexamplesofausecaseyoumightwriteforaprojecttobuildan OnlineBookstore.Thisisjustapartiallist,togiveyouanidea–andfollowsthe samestepslistedabove. 1. Createalistofactorsforonlinebookstore: Actor

TypeofActor

Consumer

People

BookstoreManager

People

BookWarehouse

Externalsystem

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3rdPartyBookList

Externalsystem

CreditCard Processor

Externalsystem

2. Createalistofgoalsforeachactor: Actor

Goal

Consumer

Browse books Searchforabook Buybook Placeorder Trackorder Cancelorder Writereview

BookstoreManager Trackorders Rundailyreports Providerefunds Moderatebookreviewsbyconsumers BookWarehouse

SendbookavailabilityinformationtoBookstore

3rdPartyBookList

Sendlistofbooksmeetingsearchcriteriato Bookstore SenddetailsofanindividualbooktoBookstore SendreviewsforanindividualbooktoBookstore

Credit Card rocessor

Send credit card validation results to Bookstore SenddailytransactionreporttoBookstore

3. Here’sthelistofusecases–createdusingthegoalslistedabove: ID

Use Case

Primary Actor

UC-1

Browse books

Consumer

UC-2

Search for a book

Consumer

UC-3

Buy book

Consumer

UC-4

Place order

Consumer

UC-5

Track order

Consumer

UC-6

Cancel order

Consumer

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UC-7

Write review

Consumer

UC-8

Track orders

Bookstore Manager

UC-9

Run daily reports

Bookstore Manager

UC-10

Provide refunds

Bookstore Manager

UC-11

Moderatebookreviewsbyconsumers

Bookstore Manager

UC-12

Sendbookavailabilityinformationto Bookstore

BookWarehouse

UC-13

Sendlistofbooksmeetingsearchcriteriato Bookstore

3rdPartyBook List

UC-14

Senddetailsofanindividualbookto Bookstore


UC-15

Sendreviewsforanindividualbookto Bookstore


UC-16

Sendcreditcardvalidationresultsto Bookstore


UC-17 SenddailytransactionreporttoBookstore


4. Prioritizetheusecases: ID

Use Case

Primary Actor Priority of UseCase

UC-1

Browse books

Consumer

P1

UC-2

Search for a book

Consumer

P1

UC-3

Buy book

Consumer

P1

UC-4

Place order

Consumer

P1

UC-5

Track order

Consumer

P1

UC-6

Cancel order

Consumer

P2

UC-7

Write review

Consumer

P2

UC-8

Track orders

Bookstore Manager

P1

UC-9

Run daily reports

Bookstore Manager

P1

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UC-10

Provide refunds

Bookstore Manager

P1

UC-11

Moderatebookreviewsby consumers

Bookstore Manager

P2

UC-12

Sendbookavailability informationtoBookstore

Book Warehouse

P1

UC-13

Sendlistofbooksmeetingsearch 3rdPartyBook criteriatoBookstore List

P1

UC-14

Senddetailsofanindividualbook 3rdPartyBook toBookstore List

P1

UC-15

Sendreviewsforanindividual booktoBookstore


P2

UC-16

Sendcreditcardvalidation resultstoBookstore


P1

UC-17

Senddailytransactionreportto Bookstore


P1

5. Fleshout eachusecase: Wewillleavethissectionasan“Exerciseforthereader”.Herearesometips: a. TakeeachusecaseinthetableaboveandQleshitoutasadetaileduse case.Includeasmuchdetailasnecessaryforyourorganizationtoact upontheseusecases–butnomore. b. Identify&documentextensionsforeachstepofeachusecase. c. Use includes&extends relationshipstolinkusecasestogether. Examplesfromthetableabove: i. UC-3 includesUC-1 ii. UC-3 includesUC-2 iii. UC-3 includesUC-4

Exercises 1)

Spend30-60minutestorecreatesteps1-4inthissectionforaspeciQic moduleofyourproduct/project.Youmaynotbeabletodothis comprehensivelyin30-60minutes–butyoushouldbeabletogetagood feel.

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11. Templates and Tools UseCaseTemplate YoucandownloadMicrosoftWordtemplateforausecasefromthefollowinglink: DownloadUseCaseTemplate–MicrosoftWord YoucanchoosetouseonlysomeoftheQieldsinthetemplate–dependingonwhat worksbestforyourteam.Toparaphrasethefamousexpertonusecases,Albert Einstein:“Keepyourusecasetemplateassimpleaspossible,butnosimpler”!;)

So[wareToolstoManageUseCases Therearethreecategoriesofsoftwaretoolsthatarecommonlyusedtomanageuse cases.Letustakealookatthemandtheirpros/cons. 1. DesktopOficeSuite ManyteamsuseMicrosoftWord,Excelandsimilartoolstocreateandmanage theirusecases. Pros:Thesetoolsarewidelyavailableandeveryoneknowshowtousethem. Cons:Itishardertocapturestructureddata,createrelationships,andmanage usecasesforlargerprojects. 2. OnlineCollaborationTools Withthegrowingpopularityofwikisandonlinecollaborationtools(suchas GoogleDocs),teamsatmanycompaniesareadaptingsuchtoolstodocument theirusecases. Pros:Thesetoolsareeasytouse,andenableonlinecollaborationinreal-time. Cons:Itishardertocapturestructureddata,createrelationships,andmanage usecasesforlargerprojects. 3. DedicatedRequirementsManagementTools Whenteamsgrowoutoftoolssuchastheoneslistedabove,theystartusing dedicatedrequirementsmanagementtoolslikeAccompa. Pros:Thesetoolsmakeitmucheasiertocapturestructureddata,create relationships,andmanageusecasesforlargerprojects.Web-basedtoolsalso enablereal-timecollaborationovertheweb.

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Cons:Thesearemoreexpensivethanthetoolslistedabove,andthereisa learningcurveforuserstolearnandusethem.

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12. Ten Do’s Hereare10bestpracticestofollowwhenyouwriteusecases. 1. Keepthereaderinmind Alwaysrememberwhyyouarewritingtheusecases–i.e.tocommunicate information(aboutfunctionalrequirements)toyourreaders. Writingclear,easytounderstandusecasesisourgoal–farmoreimportant thanrigidlyadheringtoanyrules. 2. Identifyallactors Alwaysstartbyidentifyingalltheactors.DoingagoodjobonthisistheQirst stepinensuringyoudon’tmissanyimportantfunctionalrequirements. 3. Prioritizeusecases Alwaysprioritizeyourusecases.Ideally,youshouldprioritizethembasedon theirbusinessimportance. 4. Startwiththe“Satelliteview” OnlinemapssuchasGoogleMapshavea“satelliteview”and“streetview”.The “satelliteview”providesyouabroadviewofanarea-andasyoudrilldown deeper,yougettothe“streetview”. Whenyoustartwritingusecasesforaproject,alwaysstartwith“satelliteview” –i.e.withafocusonbreadth,notdepth.Thiswillgetyougoingquickly,and helpyouavoidgettingmiredindetailsattheoutset. Asyouprogress,youcanfocusmoreandmoreondepth–i.e.deQiningthe detailsforeachusecase.Thestepsoutlinedinchapter10willhelpyoudothis. 5. Useactivevoice I’venoticedthatmanypeople(includingme)haveatendencytowritein passivevoiceorfromtheperspectiveofthesystem. Thisresultsinstepssuchas“CreditcardisveriQied”–whichdoesn’tclearly deQinewhoperformedthestep.Alwayswriteinactivevoice–forexample: “CreditcardprocessingsystemveriQiesthecreditcard”. Tip:Starteachsentencewiththenameofanactor–thiswillhelpensurean activevoice.

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6. Deinepre-conditions AlwaysdeQinepre-conditionsofeachusecase.Thishelpsthereaderunderstand thecontextoftheusecase.Evenwhenthecontextiscrystalcleartothewriter, readersareoftenconfused. 7. Deinepost-conditions AlwaysdeQinepost-conditionsofeachusecase.Thisnotonlyhelpsthereaders understandtheusecasebetter–italsoservesasa“contract”betweenthe projectteammembers. 8. Deinefailureconditions Studiesbymanyorganizations(suchasTheStandishGroup)havefound “Missedrequirements”tobeatopcauseofprojectfailures. Missedrequirementsoftenresultfromnotfullyaddressingfailureconditions. WorkwithyourteamtoidentifyallkeyfailureconditionsanddeQinethe behaviorclearly.Formostprojects,creatingusecasestoaddressfailure conditionswilltakeasmuchtimeasMSS–andoftenmuchlonger. Well-designedproducts,suchasthosefromApple,handlefailureconditionsina veryuser-friendlyfashion. 9. Writetextualusecases(Say“No”tostickigures,akaUMLdiagrams) Sometimesyoumayhearpeoplereferto“UMLDiagrams”asusecases–these arediagramscomposedofstickQigures,ellipsesandassortedother hieroglyphics(seethisblogpost foradiscussiononthistopic). Manyreadersofusecases-suchasendusers,engineers&businessexecutives- don’tknowhowtoreadUMLdiagrams.Thereisareasonwhyhumansevolved fromhieroglyphicstoalphabettext.Textiseasiertowrite&understand! Doallyourreadersafavor,andwritetextbasedusecases,inplainEnglish. WhenitcomestoUMLdiagrams,justsay“No”.Ifyou’renotconvincedyet, pleaserereadtip#1inthischapter. 10. Keepeachusecaseshort Writeshortusecases,nomorethan10-15stepsatthemost.Ifausecasegets longerthanthis,breakitupintomultipleusecases–andcreaterelationships (seechapter9)totiethemtogether. Usecaseslongerthan15stepsarehardertoread-andcausethosewhoread ourusecasestosuffertheafore-mentionedMEGO(MyEyesGlazeOver)effect!

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13. Frequently Asked Questions 1. Areusecasesconsideredrequirements? Yes,usecasesareindeedrequirements.TheyareaspeciQictypeofrequirement– referredtoas“FunctionalRequirements”. So,usecasesareusedtodocumentsome,butnotall,oftherequirementsfora softwareproject. 2. Canusecasesbeusedinagileprojects? RequirementsforanAgileprojectareusuallydocumentedviaUserStories. Pleaseseechapter2ofthisbookforadiscussionofUseCasesvs.UserStories. 3. Howdoyouwriteandmanagelargevolumesofusecases? Pleaseseechapter10ofthisbookfora5-stepprocesstowriteandmanagelarge volumesofusecases. RequirementsmanagementsoftwaresuchasAccompacanbeveryhelpfulin doingthisaswell. 4. Whatroledo“UMLDiagrams”playinusecases? Ifyou’renotfamiliarwithUMLdiagrams(luckyyou!)–theyarediagrams consistingofstickQiguresandellipses,usedbysometodocumentusecases. AlistairCockburnwondersinhispopularbook“WritingEffectiveUseCases”: “Forreasonsthatremainamysterytome,manypeoplehavefocusedonthe stickQiguresandellipsesinusecasewriting…andhaveneglectedtonotice thatusecasesarefundamentallyatextform…” IagreewithAlistair.Ibelievethebestwaytowriteusecasesisusingtextual formatdescribedinthisbook. Justsay“No”toUMLdiagrams–theyareveryhardtounderstandformost peoplewhoreadtheusecaseswewrite. 5. Shouldusecasescontainanyinformationaboutuserinterface(UI)? Usecasespuristswilltellyouthatusecasesshouldnot containanyinformation aboutuserinterfaceatall. Well,I’mnotapuristwhenitcomestousecases(orprettymuchanythingelse!). IthinkitistotallyokaytoincludesomeinformationaboutUIinyourusecases. Ultimately,itdependsonwhatmakesthemostsenseforyourprojectteam. Thatsaid,pleaserememberthatourprimarygoalinwritingusecasesisto

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documentthefunctionalrequirements–notUI. 6. Howdousecasesitintotheoverallrequirementsprocessforaproject? Increatingandmanagingrequirementsforaproject–3typesofartifactsare usuallycreatedandmanaged. a. Features High-levelfunctionalitythatasystemmustprovidetohelptheuser achieveanobjective. b. UseCases The functional requirementsneededtoimplementthefeature. c. Requirements Thenon-functionalrequirements(suchasperformance,security,UI design,scalability,etc)neededtoimplementthefeature. Pleaseseethisblogpost foramoredetaileddiscussionofofhowfeatures,use casesandrequirementsQittogether.Youmayalsowanttoreadthebook “SoftwareRequirements”byKarlWiegers(seelinkinthe“FurtherReading” chapterofthisbook)foranevenmoredetailedlookatthis. Inaddition,usecasesareusedasfollows: a. UIdesignteamscreatetheirUIdesignspeciQicationsbasedontheuse cases b. Developmentteamsbreakdowntheusecasestocreateworktasksfor developers c. Ateamscreatetestcases(forfunctionaltesting)basedontheusecases

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14. Further Reading I’venowsharedwithyouasummarizedversionofwhatI’velearnedaboutusecases throughmanyyearsofhands-onexperience,andreadingsomegreatbooks.Ihopeit helpsyouintheonlywaythatcounts–todoyourjobbetterandbuildsuccessful products. TherearemanyintheindustrywhoknowwaymoreaboutusecasesthanIdo.My reasonforwritingthisbookisthattheydon’tseemtohavewrittenashortbookthat helpspeoplequicklylearnandbeneQitfromusecases. However,someofthemhavewrittengreatbooksonthesubject–I’velistedthem below.Iencourageyoutobuyandreadeveryoneofthem. 1. WritingEffectiveUseCases-AlistairCockburn Anindispensablebookthatwillhelpyoulearnandmasterusecases.Inaddition tothisbook,Alistairhascontributedimmenselytothesubjectofusecases. 2. SoftwareRequirements-KarlWiegers ThisisagreatbookbyKarlonmanagingrequirements.Thiscoversthetopicof requirementsmanagementthoroughly,includingusecases. 3. MasteringtheRequirementsProcess-SuzanneandJamesRobertson Anexcellentbookthatcoverstherequirementsprocessend-to-end,includinga verygoodtopiconusecases. 4. AppliedSoftwareProjectManagement -AndrewStellman,JenniferGreene Thisbookcoversmanytopicsonsoftwareprojectmanagement.Itisagoodto readtounderstandhowusecasesQitintooverallprojectmanagement.

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15. Glossary Actor AhumanpersonoranExternalSystem. Extends Atypeofrelationshipusedtolinktogetherusecasesforaproject.Theother typeofrelationshipis“Includes”. Extension AScenarioduringwhichsomethinggoeswrong,orsomethingdeviatesfrom theMSS . ExternalSystem ASystemthatisoutsideoftheSUD. Goal Theobjectivethe Actorhas.Thisiswhythe Actor interactswiththeSUDin themannerdescribedinaspeciQicusecase. Includes Atypeofrelationshipusedtolinktogetherusecasesforaproject.Theother typeofrelationshipis“Extends”. MainSuccessScenario(MSS) TheScenarioinwhichnothinggoeswrong,andthePrimaryActor achieves theGoal . Post-condition ThestatethattheSUDwillendupinaftertheinteractionsdescribedinthe usecasearecompleted. Pre-condition ThestatethattheSUDwasinbeforetheinteractionsdescribedintheuse casestart. PrimaryActor The Actor whoinitiatesaninteractionwiththeSUDtoachievetheGoal . Relationship Usedtolinktogetherusecasesforaproject.Twotypesofrelationshipsare mostoftenused:Extends,Includes.

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Scenario Sequenceofinteractionsunderonecondition(suchas:UserQindsthebook he’slookingfor,UserisunabletoQindthebook,etc.).Oneormorescenarios (makingupsuccess aswellas failureconditions)makeupausecase. System Acomputer,electronicormechanicalsystem(oracombinationthereof)that iscapableofinteraction. SystemUnderDesign(SUD) TheSystemwe’redevelopingintheprojectforwhichwe’rewritingtheuse case. UseCaseID AuniqueIDassignedtoausecase.WeshouldassignauniqueIDtoeachuse casewewrite–thismakesiteasiertocommunicateaboutalistofusecases.

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eBook - The Practical Guide to Use Cases.pdf

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