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DerivingFunctionalSpeci cationsfromBusinessRequirementswithAmpersandSTEFJOOSTENOpenUniversityoftheNetherlandsOrdinaNVHowdoweknowthatafunctionalspeci cation(ofsomeinformationsystem)satis estherequire-mentsputforwardbythebusiness?Thispaperproposesamethod,Ampersand,asananswertothisproblem.Italsoproposesanaccompanyingtool,ADL,thatgeneratesdatamodels,ser-vicecataloguesandtheirspeci cations,toassistrequirementsengineersinproducingasoundfunctionalspeci cation.Ampersandimprovesthelifeofrequirementsengineersintwoways:itgivesthemthemeanstoprovebusinessrequirementsconsistentandcompleteanditgivesthemseveraldesignartifactstofacilitatetheirdiscussionswithsoftwaredesigners.Thegeneratedfunc-tionalspeci cationfeaturesplatformindependenceandprovablecompliancewiththerulesofthebusiness.Inacasestudy,asetofrequirementsispresentedtogetherwiththeformalspeci cationgen-eratedfromit.Thisexample,featuringanorder-delivery-invoiceprocess,compliesfullywiththebusinessrules.Ampersandhasbeentriedinvariouspracticalsituationswithpayingcustomersandclassroomexperiencehasshownthatthisapproachcanbetaughttobusinessanalysts.Thisevidencesupportsthefeasibilityfromapractitioner'spointofview.CategoriesandSubjectDescriptors:D.2.2[SoftwareEngineering]:DesignToolsandTech-niques;D.2.10[SoftwareEngineering]:DesignMethodologies;I.1.4[SymbolicandAlgebraicManipulation]:ApplicationsGeneralTerms:Design,LanguagesAdditionalKeyWordsandPhrases:Automateddesign,businessprocesses,businessrules,infor-mationsystemdesign,rulebaseddesign,softwareengineering,requirementsengineering.1.INTRODUCTIONRequirementsdescribetheusersintentionsexpectationsandneeds,butalsodelimittheinformationsystemneededtorealizetheseintentions.Oneofthechallengesofrequirementsengineeringistohowtounifytheinformalprocessofcapturingtheneedsofuserswiththeformalprocessofspecifyinganinformationsystem.The rstrequirescommunicativeskillsandinformaltechniques,thelatterrequiresformaltechniquestoprescribethedesiredpropertiesofaninformationsystemanditscontext.Thispaperproposestotranslatebusinessrequirementsintoafunctionalspeci cationbymeansofacompilationprocess.Thataddressesthechallengeinbottomstu Permissiontomakedigital/hardcopyofallorpartofthismaterialwithoutfeeforpersonalorclassroomuseprovidedthatthecopiesarenotmadeordistributedforpro torcommercialadvantage,theACMcopyright/servernotice,thetitleofthepublication,anditsdateappear,andnoticeisgiventhatcopyingisbypermissionoftheACM,Inc.Tocopyotherwise,torepublish,topostonservers,ortoredistributetolistsrequirespriorspeci cpermissionand/orafee.c20YYACM0000-0000/20YY/0000-0001$5.00ACMJournalName,Vol.V,No.N,Month20YY,Pages1{27.2StefJoostentwoways.Onetheuserside,businessrequirementscanbekeptentirelyinnaturallanguage.Onthetechnicalside,thefunctionalspeci cationcanbeentirelyformal.Thecompilerguaranteescompliancebetweenthetwo.Thecontributionofthisarticleconsistsofamethod,Ampersand,andanaccom-panyingtool,ADL,bothintendedforrequirementsengineers.Fromagivensetofformallyde nedbusinessrequirements,ADLgeneratesafunctionalspeci cationconsistingofadatamodel,aservicecatalogue,aformalspeci cationoftheser-vices,andafunctionpointanalysis.Newtothisapproachistheuseofrelationalgebraforrequirementselicitation.Eachrequirementisrepresentedasaruleinrelationalgebra,whichservesasaninvarianttobesatis edbythebusiness.Wecalltheserules`businessrule'toindicatethatitisownedandmotivatedbythebusiness.Theone-to-onecorrespondenceofabusinessrequirementwithabusinessruleo erstraceability.ADLtranslatesbusinessrulesbackintothenaturallan-guage,providingadequatefeedbacktotherequirementsengineerforvalidatinghiswork.ADLalsotranslatestheentiresetofrequirementstodesignartifactsthatarerequiredinthesubsequentsoftwareengineeringprocess.Inthisarticleweconsidereveryactivitythatprecedessoftwaredesigntobeinthescopeofrequirementsengineering.Adistinctionismadebetweendescriptiveandprescriptiveactivities[Greenspanetal.1994].Thisarticleusesthewordre-quirementinadescriptivesense,todescribeanexplicitorimplicitneedofusers.Ontheotherhand,thewordspeci cationisusedtoprescribepropertiesofasystemtobebuilt.Thephrasefunctionalspeci cationdenotesaprescriptionofdesiredfunc-tionality,andanon-functionalspeci cationprescribesanyotherdesiredquality,suchasaperformanceproperty,asecurityproperty,oraneciencyproperty.Manyattemptshavebeenmadetoformalizefunctionalspeci cations,suchasZ[Spivey1992],CSP[Roscoeetal.1997],LOTOS[ISO1987],VDM[Jones1986],Larch[GuttagandHorning1993],butthenumberofattemptstoformalizerequire-mentsarefewerandlessknown[Borgidaetal.1985;?;?].Stillthereareanumberofgoodreasonstoformalizerequirementstoo.ThesereasonsformtherationalefordevelopingAmpersand:|Aformallydenotedrequirementisinherentlyfalsi able.Aninformalrequirementisnotnecessarilyfalsi able,makingitunsurewhethersucharequirementcanbeusedobjectivelyasacriterionofsatisfaction.Aformalstatementthathastobekepttrueduringthelifetimeoftheinformationsystem,providesrequirementsengineerswithanobjectivesatisfactioncriterion.|Requirementsarecompositional.Aspeci cationisnot.Addinganddro