Database Modeling and Design

4
Requirements Analysis and
Conceptual Data Modeling
T
his chapter shows how the ER and UML approaches can be applied
to the database life cycle, particularly in steps I through II(b) (as
defined in Section 1.2), which include the requirements analysis and
conceptual data modeling stages of logical database design. The example
introduced in Chapter 2 is used again to illustrate the ER modeling principles
developed in this chapter.
4.1 Introduction
Logical database design is accomplished with a variety of approaches,
including the top-down, bottom-up, and combined methodologies. The
traditional approach, particularly for relational databases, has been a
low-level, bottom-up activity, synthesizing individual data elements into
normalized tables after carefully analyzing the data element interdependencies
defined during the requirements analysis. Although the traditional
process has been somewhat successful for small- to medium-sized
databases, when used for large databases its complexity can be overwhelming
to the point where practicing designers do not bother to use it
with any regularity. In practice, a combination of the top-down and bottom-up
approaches is used; in most cases, tables can be defined directly
from the requirements analysis.
The conceptual data model has been most successful as a tool for
communication between the designer and the end user during the
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