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

AppendixfCfThefUniversityfLab:
ConceptualfDesignfVerification,fLogicalfDesign,fandfImplementation

Appendix C

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



DiscussionfFocus


Howfisfafdatabasefdesignfverified,fandfwhyfisfsuchfverificationfnecessary?



Usefourfdetailedfanswerftofquestionf1ftoffocusfclassfdiscussionfonfdatabasefdesignfverification.fStressfthatf
thefverificationfprocessfusesfthefinitialfERfmodelfasfafcommunicationftool.



Thefdesignerfmayfbeginfthefverificationfprocessfbyfdescribingftheforganization'sfoperationsftofitsfendfuser
s,fbasingfthefdetailedfdescriptionfonfthefinitialfERfmodel.fNext,fexplainfhowfthefoperationsfwillfbefsupporte
dfbyfthefdatabasefdesign.fStressfthatfthefdesignfmustfsupportfthefend-
userfapplicationfviews,foutputs,fandfinputs.fPointsftofbefaddressedfincludefsuchfquestionsfas:

 Isfthefdescriptionfaccurate?fIffnot,fwhatfaspectsfoffthefdescriptionfmustfbefcorrected?
 Doesf thef modelf supportf thef end-userf requirements?f Iff not,f whatf aspectsf off thef end-
userfrequirementsfhavefnotfbeenfaddressedforfhavefbeenfaddressedfinadequately?


Keepf infmindf thatf evenf af modelf thatf perfectlyf addressesf allf initiallyf determinedfendf userf requirementsfisfl
ikelyftofneedfadjustmentsfasfthosefendfusersfbeginftofunderstandftheframificationsfoffthefdatabasefdesign'
sfcapabilities.fInfmanyfcases,fthefendfusersfmayflearnfwhatftheforganization'sfprocessesfandfproceduresfac
tuallyfare,fthusfleadingftofnewfrequirementsfandfthefperceptionfoffnewfopportunities.fThefdatabasefdesign
erfmustfkeepfsuchflikelyfdevelopmentsfinfmind,fespeciallyfiff(s)hefworksfasfafdatabasefdesignfconsultant.f(
Anticipationfoffsuchfdevelopmentsfmustfbeffactoredfintofthefcontractfnegotiationsfforfconsultingffees.)



Discussfthefrolefoffthefsystemfmodules.




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, AppendixfCfThefUniversityfLab:
ConceptualfDesignfVerification,fLogicalfDesign,fandfImplementation


Thef usef off systemf modulesf canf hardlyf bef overemphasizedf inf af databasef designf environment.f Stressfth
esefmodulefcharacteristicsfandffeatures:

 Modulesfrepresentfsubsetsfoffthefdatabasefmodel:fSmallerf"pieces"farefmorefeasilyfundersto
od.
 Modulesfarefself-
containedfandfaccomplishfafspecificfsystemffunction;fiffsuchfafsystemffunctionfmustfbefmod
ified,fotherffunctionsfremainfunaffected.
 Modulesffitfintofafmodularfdatabasefdesign,fwhichfisfmorefeasilyfmodifiedfandfadaptedftofne
wfcircumstances.fBecausefmodificationfeffortsfareffocusedfonfafdatabasefsubset,fproductivit
yfoffbothfdesignersfandfapplicationfdevelopersfisflikelyftofbefenhanced.


Modulefinterfacesfmustfbefclearfiffthefmodulesfarefexpectedftofworkfwellfwithinfthefoverallfsystem.




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, AppendixfCfThefUniversityfLab:
ConceptualfDesignfVerification,fLogicalfDesign,fandfImplementation

AnswersftofReviewfQuestions


1. Whyfmustfafconceptualfmodelfbefverified?fWhatfstepsfarefinvolvedfinfthefverificationfprocess?


Thefverificationfoffafconceptualfmodelfisfcrucialftofafsuccessfulfdatabasefdesign.fThefverificationfproce
ssfallowsfthefdesignerftofcheckfthefaccuracyfoffthefdatabasefdesignfby:

 Re-examiningfdatafandfdataftransformations.
 Enablingf thef designerf tof evaluatef thef designf efficiencyf relativef tof thef endf user'sf andfsy
stem'sfdesignfgoals.


Keepfinfmindfthat,ftofaflargefextent,fthefbestfdesignfisfthefonefthatfservesfthef end-
userfrequirementsfbest.fForfexample,fafdesignfthatfworksfwellfforfafmanufacturingffirmfmayfnotffitfthef
needsfoffafmarketingfresearchffirm,fandfvicefversa.



Thefverificationfprocessfhelpsfthefdesignerftofavoidfimplementationfproblemsflaterfby:

 Validatingfthefmodel'sfentities.f(Rememberfthefminimalfdatafrule.)
 Confirmingfentityfrelationshipsfandfeliminatingfduplicate,funnecessary,forfimproperlyfd
efinedfrelationships.
 Eliminatingfdatafredundancies.
 Improvingfthefmodel'sfsemanticfprecisionftofbetterfrepresentfreal-worldfoperations.
 Confirmingfthatfallfuserfrequirementsf(processing,fperformance,forfsecurity)farefmet.


Verificationfisfafcontinuousfactivityfinfanyfdatabasefdesign.fThefdatabasefdesignfprocessfisfevolutionar
yfinfnature:fItfrequiresfthefcontinuousfevaluationfoffthefdevelopingfmodelfbyfexaminingfthefeffectfoffa
ddingfnewfentitiesfandfbyfconfirmingfthatfanyfdesignfchangesfenhancefthefmodel'sfaccuracy.



Thefverificationfprocessfrequiresftheffollowingfsteps:



1. Identifyfthefdatabase'sfcentralfentity.


Thef centralf entityf isf thef mostf importantf entityf inf ourf database,f andf mostf off thef otherfen
titiesfdependfonfit.




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, AppendixfCfThefUniversityfLab:
ConceptualfDesignfVerification,fLogicalfDesign,fandfImplementation


2. Identifyfandfdefinefeachfmodulefandfitsfcomponents.


Thef designerf dividesf thef databasef modelf intof smallerf setsf thatf reflectf thef dataf needsf offpa
rticularfsystemsfmodulesfsuchfasfinventory,forders,fpayroll,fetc.



3. Identifyfandfdefinefeachfoffthefmodule'sfprocesses.


Specifically,f thisf stepf requiresf thef identificationf andf definitionf off thef databasef transactions
thatfrepresentfthefmodule'sfreal-worldfoperations.




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