Databases Reference
In-Depth Information
Chapter 6
One Concept Equals
One Data Element:
A Rule for Developing
Data Elements
Jennifer Little
D
.
A data element is
the smallest unit used to collect and document these facts. Data elements
specify the rules to which data must conform, thereby establishing the
structure of the data. For example, the data element in Exhibit 1 establishes
the structure in which people's last names are stored in a particular infor-
mation system.
ATA
REPRESENTS
SEPARATE
FACTS
ABOUT
OBJECTS
Because data elements provide structure for the data, poorly designed
data elements lead to poor quality data. The most fundamental data ele-
ment design principle is that a data element should encompass only one
concept. Following the one-concept-equals-one-data-element rule when
developing data elements can help ensure quality data elements. The rule
can also help revise data elements during reengineering efforts to identify
and improve problem data structures.
A data element has several parts (e.g., data element name, length, defi-
nition, format, and valid values), which are called data element attributes.
When new data elements are developed, each attribute should be created
to abide by the one-concept-equals-one-data-element rule. Also, when
existing data elements are revised, the attributes can be examined to
ensure that they conform to the rule. It is particularly critical to apply the
one-concept-equals-one-data-element rule to two data element attributes
— name and valid values. This chapter examines these two data element
attributes and suggests ways to ensure compliance with the rule.
Search WWH ::
Custom Search