Solutions Manual for Database Systems: Design, Implementation, & Management (12th Edition) by Carlos Coronel | Complete Chapter Solutions

Appendix C The University Lab: b b b b




Conceptual Design Verification, Logical Design, and Implementation b b b b b b




Appendix C b




The University Lab: Conceptual Design, b b b b




Verification,Logical Design, and Implementation
b b b b b




Discussion Focus b




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




Use our detailed answer to question 1 to focus class discussion on database design verification. Stress that
b b b b b b b b b b b b b b b b




the verification process uses the initial ER model as a communication tool.
b b b b b b b b b b b b




The designer may begin the verification process by describing the organization's operations to its end users,
b b b b b b b b b b b b b b b




basing the detailed description on the initial ER model. Next, explain how the operations will be supported
b b b b b b b b b b b b b b b b b




by the database design. Stress that the design must support the end-user application views, outputs, and
b b b b b b b b b b b b b b b b




inputs. Points to be addressed include such questions as:
b b b b b b b b b




 Is the description accurate? If not, what aspects of the description must be corrected?
b b b b b b b b b b b b b




 Does the model support the end-user requirements? If not, what aspects of the end-
b b b b b b b b b b b b b




userrequirements have not been addressed or have been addressed inadequately?
b b b b b b b b b b




Keep in mind that even a model that perfectly addresses all initially determined end user requirementsis
b b b b b b b b b b b b b b b b




likely to need adjustments as those end users begin to understand the ramifications of the database
b b b b b b b b b b b b b b b b




design's capabilities. In many cases, the end users may learn what the organization's processes and
b b b b b b b b b b b b b b b




procedures actually are, thus leading to new requirements and the perception of new opportunities.
b b b b b b b b b b b b b b




Thedatabase designer must keep such likely developments in mind, especially if (s)he works as a database
b b b b b b b b b b b b b b b b b




design consultant. (Anticipation of such developments must be factored into the contract negotiations for
b b b b b b b b b b b b b b




consulting fees.)
b b




Discuss the role of the system modules.
b b b b b b




1

, Appendix C The University Lab: b b b b




Conceptual Design Verification, Logical Design, and Implementation
b b b b b b




The use of system modules can hardly be overemphasized in a database design environment.
b b b b b b b b b b b b b




Stressthese module characteristics and features:
b b b b b b




 Modules represent subsets of the database model: Smaller "pieces" are more
b b b b b b b b b b




easilyunderstood.
b b




 Modules are self-contained and accomplish a specific system function; if such a system
b b b b b b b b b b b b




function must be modified, other functions remain unaffected.
b b b b b b b b




 Modules fit into a modular database design, which is more easily modified and adapted tonew
b b b b b b b b b b b b b b b




circumstances. Because modification efforts are focused on a database subset, productivity
b b b b b b b b b b b




of both designers and application developers is likely to be enhanced.
b b b b b b b b b b b




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




2

, Appendix C The University Lab: b b b b




Conceptual Design Verification, Logical Design, and Implementation b b b b b b




Answers to Review Questions b b b




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




The verification of a conceptual model is crucial to a successful database design. The verification
b b b b b b b b b b b b b b




process allows the designer to check the accuracy of the database design by:
b b b b b b b b b b b b b




 Re-examining data and data transformations. b b b b




 Enabling the designer to evaluate the design efficiency relative to the end user's
b b b b b b b b b b b b




andsystem's design goals.
b b b b




Keep in mind that, to a large extent, the best design is the one that serves the end-user requirements
b b b b b b b b b b b b b b b b b b




best. For example, a design that works well for a manufacturing firm may not fit the needs of a
b b b b b b b b b b b b b b b b b b b




marketing research firm, and vice versa.
b b b b b b




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




 Validating the model's entities. (Remember the minimal data rule.)
b b b b b b b b




 Confirming entity relationships and eliminating duplicate, unnecessary, or b b b b b b b




improperlydefined relationships.
b b b




 Eliminating data redundancies. b b




 Improving the model's semantic precision to better represent real-world operations.
b b b b b b b b b




 Confirming that all user requirements (processing, performance, or security) are met.
b b b b b b b b b b




Verification is a continuous activity in any database design. The database design process is evolutionary
b b b b b b b b b b b b b b




in nature: It requires the continuous evaluation of the developing model by examining the effect of
b b b b b b b b b b b b b b b b




adding new entities and by confirming that any design changes enhance the model's accuracy.
b b b b b b b b b b b b b b




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




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




The central entity is the most important entity in our database, and most of the
b b b b b b b b b b b b b b




botherentities depend on it. b b b b




3

, Appendix C The University Lab: b b b b




Conceptual Design Verification, Logical Design, and Implementation
b b b b b b




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




The designer divides the database model into smaller sets that reflect the data needs
b b b b b b b b b b b b b




ofparticular systems modules such as inventory, orders, payroll, etc.
b b b b b b b b b b




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




Specifically, this step requires the identification and definition of the database transactions
b b b b b b b b b b b




that represent the module's real-world operations.
b b b b b




4