Appendix C The University Lab: Conceptual Design, Verification, Logical Design, and Implementation

AppendixeCeTheeUniversityeLab:
ConceptualeDesigneVerification,eLogicaleDesign,eandeImplementation

Appendix C

The University Lab: Conceptual Design, Verification,
Logical Design, and Implementation



DiscussioneFocus


Howeiseaedatabaseedesigneverified,eandewhyeisesucheverificationenecessary?



Useeouredetailedeansweretoequestione1etoefocuseclassediscussioneonedatabaseedesigneverification.eStresse
thatetheeverificationeprocesseusesetheeinitialeERemodeleaseaecommunicationetool.



Theedesigneremayebeginetheeverificationeprocessebyedescribingetheeorganization'seoperationsetoeitseendeu
sers,ebasingetheedetailededescriptioneonetheeinitialeERemodel.eNext,eexplainehowetheeoperationsewillebees
upportedebyetheedatabaseedesign.eStressethatetheedesignemustesupportetheeend-
usereapplicationeviews,eoutputs,eandeinputs.ePointsetoebeeaddressedeincludeesuchequestionseas:

 Isetheedescriptioneaccurate?eIfenot,ewhateaspectseofetheedescriptionemustebeecorrected?
 Doese thee modele supporte thee end-usere requirements?e Ife not,e whate aspectse ofe thee end-
usererequirementsehaveenotebeeneaddressedeorehaveebeeneaddressedeinadequately?


Keepe ine minde thate evene ae modele thate perfectlye addressese alle initiallye determinede ende usere requiremen
tseiselikelyetoeneedeadjustmentseasethoseeendeusersebeginetoeunderstandetheeramificationseofetheedatabas
eedesign'secapabilities.eInemanyecases,etheeendeusersemayelearnewhatetheeorganization'seprocesseseandep
rocedureseactuallyeare,ethuseleadingetoenewerequirementseandetheeperceptioneofeneweopportunities.eTh
eedatabaseedesigneremustekeepesuchelikelyedevelopmentseinemind,eespeciallyeife(s)heeworkseaseaedatabas
eedesigneconsultant.e(Anticipationeofesuchedevelopmentsemustebeefactoredeintoetheecontractenegotiation
seforeconsultingefees.)



Discussetheeroleeofetheesystememodules.



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, AppendixeCeTheeUniversityeLab:
ConceptualeDesigneVerification,eLogicaleDesign,eandeImplementation


Thee usee ofe systeme modulese cane hardlye bee overemphasizede ine ae databasee designe environment.e Stre
ssetheseemoduleecharacteristicseandefeatures:

 Moduleserepresentesubsetseofetheedatabaseemodel:eSmallere"pieces"eareemoreeeasilyeunderst
ood.
 Moduleseareeself-
containedeandeaccomplisheaespecificesystemefunction;eifesucheaesystemefunctionemustebeem
odified,eotherefunctionseremaineunaffected.
 Modulesefiteintoeaemodularedatabaseedesign,ewhicheisemoreeeasilyemodifiedeandeadaptedetoe
newecircumstances.eBecauseemodificationeeffortseareefocusedeoneaedatabaseesubset,eproduc
tivityeofebothedesignerseandeapplicationedeveloperseiselikelyetoebeeenhanced.


Moduleeinterfacesemustebeecleareifetheemoduleseareeexpectedetoeworkewellewithinetheeoverallesystem.




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, AppendixeCeTheeUniversityeLab:
ConceptualeDesigneVerification,eLogicaleDesign,eandeImplementation

AnswersetoeRevieweQuestions


1. Whyemusteaeconceptualemodelebeeverified?eWhatestepseareeinvolvedeinetheeverificationeprocess?


Theeverificationeofeaeconceptualemodeleisecrucialetoeaesuccessfuledatabaseedesign.eTheeverificationepr
ocesseallowsetheedesigneretoechecketheeaccuracyeofetheedatabaseedesigneby:

 Re-examiningedataeandedataetransformations.
 Enablinge thee designere toe evaluatee thee designe efficiencye relativee toe thee ende user'se andes
ystem'sedesignegoals.


Keepeinemindethat,etoeaelargeeextent,etheebestedesigneisetheeoneethateservesethee end-
usererequirementsebest.eForeexample,eaedesignethateworksewelleforeaemanufacturingefirmemayenotefit
etheeneedseofeaemarketingeresearchefirm,eandeviceeversa.




Theeverificationeprocessehelpsetheedesigneretoeavoideimplementationeproblemselatereby:

 Validatingetheemodel'seentities.e(Rememberetheeminimaledataerule.)
 Confirmingeentityerelationshipseandeeliminatingeduplicate,eunnecessary,eoreimproperlye
definederelationships.
 Eliminatingedataeredundancies.
 Improvingetheemodel'sesemanticeprecisionetoebettererepresentereal-worldeoperations.
 Confirmingethatealleusererequirementse(processing,eperformance,eoresecurity)eareemet.


Verificationeiseaecontinuouseactivityeineanyedatabaseedesign.eTheedatabaseedesigneprocesseiseevolutio
naryeinenature:eIterequiresetheecontinuouseevaluationeofetheedevelopingemodelebyeexaminingetheeeff
ecteofeaddingeneweentitieseandebyeconfirmingethateanyedesignechangeseenhanceetheemodel'seaccurac
y.



Theeverificationeprocesserequiresetheefollowingesteps:



1. Identifyetheedatabase'secentraleentity.


Thee centrale entitye ise thee moste importante entitye ine oure database,e ande moste ofe thee oth
ereentitiesedependeoneit.



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, AppendixeCeTheeUniversityeLab:
ConceptualeDesigneVerification,eLogicaleDesign,eandeImplementation


2. Identifyeandedefineeeachemoduleeandeitsecomponents.


Thee designere dividese thee databasee modele intoe smallere setse thate reflecte thee datae needse
ofeparticularesystemsemodulesesucheaseinventory,eorders,epayroll,eetc.



3. Identifyeandedefineeeacheofetheemodule'seprocesses.


Specifically,e thise stepe requirese thee identificatione ande definitione ofe thee databasee transactions
thaterepresentetheemodule'sereal-worldeoperations.




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