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

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

Appendix C --




The University Lab: Conceptual Design, Verification,
-- -- -- -- -- -




Logical Design, and Implementation
-- -- --




Discussion Focus --




How--is--a--database--design--verified,--and--why--is--such--verification--necessary?



Use--our--detailed--answer--to--question--1--to--focus--class--discussion--on--database--design--verification.--Stress--
that--the--verification--process--uses--the--initial--ER--model--as--a--communication--tool.



The--designer--may--begin--the--verification--process--by--describing--the--organization's--operations--to--its--end--
users,--basing--the--detailed--description--on--the--initial--ER--model.--Next,--explain--how--the--operations--will--be--
supported--by--the--database--design.--Stress--that--the--design--must--support--the--end-user--application--views,-
-outputs,--and--inputs.--Points--to--be--addressed--include--such--questions--as:




• Is--the--description--accurate?--If--not,--what--aspects--of--the--description--must--be--corrected?
• Does- - the- - model- - support- - the- - end-user- - requirements?- - If- - not,- - what- - aspects- - of- - the- -
end-user-requirements--have--not--been--addressed--or--have--been--addressed--inadequately?


Keep-- in-- mind-- that-- even-- a-- model-- that-- perfectly-- addresses-- all-- initially-- determined-- end-- user--
requirements-is--likely--to--need--adjustments--as--those--end--users--begin--to--understand--the--ramifications--of--
the--database--design's--capabilities.--In--many--cases,--the--end--users--may--learn--what--the--organization's--
processes--and--procedures--actually--are,--thus--leading--to--new--requirements--and--the--perception--of--new--
opportunities.--The-database--designer--must--keep--such--likely--developments--in--mind,--especially--if--(s)he--
works--as--a--database--design--consultant.--(Anticipation--of--such--developments--must--be--factored--into--the--
contract--negotiations--for--consulting--fees.)



Discuss--the--role--of--the--system--modules.



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Conceptual--Design--Verification,--Logical--Design,--and--Implementation


The- - use- - of- - system- - modules- - can- - hardly- - be- - overemphasized- - in- - a- - database- - design- - environment.- -
Stress-these--module--characteristics--and--features:

• Modules--represent--subsets--of--the--database--model:--Smaller--"pieces"--are--more--easily-
understood.
• Modules--are--self-contained--and--accomplish--a--specific--system--function;--if--such--a--system--
function--must--be--modified,--other--functions--remain--unaffected.
• Modules--fit--into--a--modular--database--design,--which--is--more--easily--modified--and--adapted--
to-new--circumstances.--Because--modification--efforts--are--focused--on--a--database--subset,--
productivity--of--both--designers--and--application--developers--is--likely--to--be--enhanced.


Module--interfaces--must--be--clear--if--the--modules--are--expected--to--work--well--within--the--overall--system.




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Conceptual--Design--Verification,--Logical--Design,--and--Implementation

Answers to Review Questions
-- -- --




1. Why--must--a--conceptual--model--be--verified?--What--steps--are--involved--in--the--verification--process?


The--verification--of--a--conceptual--model--is--crucial--to--a--successful--database--design.--The--verification--
process--allows--the--designer--to--check--the--accuracy--of--the--database--design--by:

• Re-examining--data--and--data--transformations.
• Enabling- - the- - designer- - to- - evaluate- - the- - design- - efficiency- - relative- - to- - the- - end- - user's- -
and-system's--design--goals.


Keep--in--mind--that,--to--a--large--extent,--the--best--design--is--the--one--that--serves--the- - end-user--
requirements--best.--For--example,--a--design--that--works--well--for--a--manufacturing--firm--may--not--fit--the--
needs--of--a--marketing--research--firm,--and--vice--versa.



The--verification--process--helps--the--designer--to--avoid--implementation--problems--later--by:

• Validating--the--model's--entities.--(Remember--the--minimal--data--rule.)
• Confirming--entity--relationships--and--eliminating--duplicate,--unnecessary,--or--
improperly-defined--relationships.
• Eliminating--data--redundancies.
• Improving--the--model's--semantic--precision--to--better--represent--real-world--operations.
• Confirming--that--all--user--requirements--(processing,--performance,--or--security)--are--met.


Verification--is--a--continuous--activity--in--any--database--design.--The--database--design--process--is--
evolutionary--in--nature:--It--requires--the--continuous--evaluation--of--the--developing--model--by--
examining--the--effect--of--adding--new--entities--and--by--confirming--that--any--design--changes--enhance--
the--model's--accuracy.



The--verification--process--requires--the--following--steps:



1. Identify--the--database's--central--entity.


The- - central- - entity- - is- - the- - most- - important- - entity- - in- - our- - database,- - and- - most- - of- -
the- - othere- ntities--depend--on--it.



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Conceptual--Design--Verification,--Logical--Design,--and--Implementation


2. Identify--and--define--each--module--and--its--components.


The- - designer- - divides- - the- - database- - model- - into- - smaller- - sets- - that- - reflect- - the- - data- -
needs- - ofp
- articular--systems--modules--such--as--inventory,--orders,--payroll,--etc.




3. Identify--and--define--each--of--the--module's--processes.


Specifically,- - this- - step- - requires- - the- - identification- - and-- definition-- of-- the- - database- - transactions
that--represent--the--module's--real-world--operations.




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