One Concept Equals One Data Element: A Rule for Developing Data Elements - High-Performance Web Databases: Design, Development, and Deployment - page 78

Exhibit 6-3. Monthly productivity information.

Name Definition

MONTHLY AVERAGE OUTPUT The average number of widgets produced per month.

Twelve occurrences are allowed.

AVERAGE OUTPUT MONTH The month for which the average number of widgets is

recorded for the employee.

Exhibit 6-4. Revised productivity report.

Name Definition

WIDGETS PRODUCED COUNT The number of widgets produced by an employee per

day. There is an unlimited number of occurrences
allowed of this data element.

WIDGETS PRODUCED DATE The sate (YYYYMMDD) on which the widgets were

produced by an employee.

the division received and its productivity; it also benefits other managers in
the organization with different information requirements. In other words,
more questions can be answered with the data.

AN ANALOGY

An anecdote about building a house offers helpful analogies regarding
the lack of flexibility caused by not following the one-concept-equals-one-
data-element rule. After determining requirements for the house, it is
decided that prefabricated house components will meet the needs in the
easiest, cheapest, and fastest way. Prefabricated parts are melded compo-
nents; and like melded data chunks, they contain more than one concept
(i.e., component).

The house is built, and construction was cheap, fast, and easy. Two
years later, however, it is decided to add an office with a separate entrance
and a security system. Because the house was built with prefabricated
parts, it is more complicated to make the addition. The prefabricated parts
are melded components; consequently, an entire side of the house must be
removed and rebuilt to accommodate the addition. Unfortunately, using
the prefabricated components to begin with was faster, cheaper, and easier
until changes needed to be made. The melded components' lack of flexibil-
ity caused the increased cost.

The Bottom Line

How can things (e.g., buildings or information) that have maximum
flexibility for the future be created within today's budget? Large building