Draw data flow diagram and system flow charts

Chapter 9 Database Design

Chapter 9

 It provides the tools and conditions to manage both data and information.

Basically, a database is a fact (data) repository that serves an information system. If the database is designed poorly, one can hardly expect that the data/information transformation will be successful, nor is it reasonable to expect efficient and capable management of data and information.

The last point deserves emphasis: even the best-designed database lacks value if it fails to meet information system objectives. In short, good database designers must pay close attention to the information system requirements.

Systems design and database design are usually tightly intertwined and are often performed in parallel. Therefore, database and systems designers must cooperate and coordinate to yield the best possible information system.

Chapter 9 Database Design

Suggestion: Use Figure 9.14 as the basis for this discussion.

In spite of the frequent arguments concerning the best design approach, perhaps the top-down vs. bottom-up distinction is quite artificial. The text's note is worth repeating:

NOTE
Even if a generally top-down approach is selected, the normalization process that revises existing table structures is (inevitably) a bottom-up technique. E-R models constitute a top-down process even if the selection of attributes and entities may be described as bottom-up. Since both the E-R model and normalization techniques form the basis for most designs, the top-down vs. bottom-up debate may be based on a distinction without a difference.

You have been contacted by the manager of one of the centers to design and implement a computerized system. Given the preceding information, do the following:

107

__4__ Create a description of each system process.

__1_ Test the system.

__1__ Interview the shop manager.

ANALYSIS
1. Interview the shop manager
2. Interview the mechanics
3. Obtain a general description of company operations 4. Create a description of each system process

Describe the vari ous modules that you believe the system should include.

We have illustrated the Information System's main modules in Figure P9.1B.

The data dictionary makes it easier to check for the existence of synonyms and homonyms, to check whether all attributes exist to support required reports, to verify appropriate relationship representations, and so on. Therefore, the data dictionary's contents will help us to provide consistency across modules and to evaluate the system's ability to generate the required reports.

In addition, the use of the data dictionary facilitates the creation of system documentation.

REPORT 1
Monthly Activity contains a summary of service categories by branch and by month. Such reports may become the basis for forecasting personnel and stock requirements for each branch and for each period.

REPORT 2
Mechanic Summary Sheet contains a summary of work hours clocked by each mechanic. This report would be generated weekly and would be useful for payroll and maintenance personnel scheduling purposes.

Sample questions and their likely impact on the design might be:
 Do you want to develop the database for all departments at once, or do you want to design and implement the database for one department at a time?

 How will the design approach affect the design process? (In other words, assess top-down vs.

The answers to such questions affect the conceptual and logical database design, the database’s implementation, its testing, and its subsequent operation.

110

As is true for the SDLC, the DBLC is not a function of the kind and extent of the collected information. Thus, the DBLC phases and their activities remain as shown:
DATABASE INITIAL STUDY
Analyze the company situation
Define problems and constraints
Define objectives
Define scope and boundaries
DATABASE DESIGN
Create the conceptual design
Create the logical design
create the physical design
IMPLEMENTATION AND LOADING
Install the DBMS
Create the database(s)
Load or convert the data
TESTING AND EVALUATION
Test the database
Fine-tune the database
Evaluate the database and its application programs
OPERATION
Produce the required information flow
MAINTENANCE AND EVOLUTION
Introduce changes
Make enhancements

111

b. The company is expanding into a new type of service and this will require to enhancing the system with a new set of tables to support this new service and integrate it with the existing data.

This is a change to enhance the system – perfective maintenance.

_4__ Create a description of each system process.

_11_ Test the system.

_2__ Interview the soccer club director of coaching.

__8_ Create the file (table) structures.

DESIGN

112