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.
1
,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.
2
,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 other
entities depend on it.
3
, 2. Identify and define each module and its components.
The designer divides the database model into smaller sets that reflect the data needs of
particular 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.
4
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.
1
,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.
2
,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 other
entities depend on it.
3
, 2. Identify and define each module and its components.
The designer divides the database model into smaller sets that reflect the data needs of
particular 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.
4
