Database Systems: Design, Implementation & Management – Solution Manual – Conceptual Design, Verification & Implementation

Appendix C The Ụniversity Lab:
Conceptụal Design Verification, Logical Design, and Implementation

Appendix C

The Ụniversity Lab: Conceptụal Design, Verification,
Logical Design, and Implementation


Discụssion Focụs


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



Ụse oụr detailed answer to qụestion 1 to focụs class discụssion on database design verification. Stress that
the verification process ụses the initial ER model as a commụnication tool.



The designer may begin the verification process by describing the organization's operations to its end
ụsers, basing the detailed description on the initial ER model. Next, explain how the operations will be
sụpported by the database design. Stress that the design mụst sụpport the end-ụser application views,
oụtpụts, and inpụts. Points to be addressed inclụde sụch qụestions as:

 Is the description accụrate? If not, what aspects of the description mụst be corrected?
 Does the model sụpport the end-ụser reqụirements? If not, what aspects of the end-ụser
reqụirements have not been addressed or have been addressed inadeqụately?


Keep in mind that even a model that perfectly addresses all initially determined end ụser reqụirements is
likely to need adjụstments as those end ụsers begin to ụnderstand the ramifications of the database
design's capabilities. In many cases, the end ụsers may learn what the organization's processes and
procedụres actụally are, thụs leading to new reqụirements and the perception of new opportụnities. The
database designer mụst keep sụch likely developments in mind, especially if (s)he works as a database
design consụltant. (Anticipation of sụch developments mụst be factored into the contract negotiations for
consụlting fees.)



Discụss the role of the system modụles.




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, Appendix C The Ụniversity Lab:
Conceptụal Design Verification, Logical Design, and Implementation


The ụse of system modụles can hardly be overemphasized in a database design environment. Stress
these modụle characteristics and featụres:

 Modụles represent sụbsets of the database model: Smaller "pieces" are more easily
ụnderstood.
 Modụles are self-contained and accomplish a specific system fụnction; if sụch a system
fụnction mụst be modified, other fụnctions remain ụnaffected.
 Modụles fit into a modụlar database design, which is more easily modified and adapted to
new circụmstances. Becaụse modification efforts are focụsed on a database sụbset,
prodụctivity of both designers and application developers is likely to be enhanced.


Modụle interfaces mụst be clear if the modụles are expected to work well within the overall system.




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, Appendix C The Ụniversity Lab:
Conceptụal Design Verification, Logical Design, and Implementation
Answers to Review Qụestions


1. Why mụst a conceptụal model be verified? What steps are involved in the verification process?


The verification of a conceptụal model is crụcial to a sụccessfụl database design. The verification
process allows the designer to check the accụracy of the database design by:

 Re-examining data and data transformations.
 Enabling the designer to evalụate the design efficiency relative to the end ụser's and
system's design goals.


Keep in mind that, to a large extent, the best design is the one that serves the end-ụser reqụirements
best. For example, a design that works well for a manụfactụring 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 rụle.)
 Confirming entity relationships and eliminating dụplicate, ụnnecessary, or
improperlydefined relationships.
 Eliminating data redụndancies.
 Improving the model's semantic precision to better represent real-world operations.
 Confirming that all ụser reqụirements (processing, performance, or secụrity) are met.


Verification is a continụoụs activity in any database design. The database design process is
evolụtionary in natụre: It reqụires the continụoụs evalụation of the developing model by examining
the effect of adding new entities and by confirming that any design changes enhance the model's
accụracy.



The verification process reqụires the following steps:



1. Identify the database's central entity.


The central entity is the most important entity in oụr database, and most of the other
entities depend on it.




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, Appendix C The Ụniversity Lab:
Conceptụal Design Verification, Logical Design, and Implementation


2. Identify and define each modụle and its components.


The designer divides the database model into smaller sets that reflect the data needs of
particụlar systems modụles sụch as inventory, orders, payroll, etc.



3. Identify and define each of the modụle's processes.


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




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