Databases Reference
In-Depth Information
Chapter 5
A Framework for
Classifying Data
William H. Inmon
A
USEFUL
VEHICLE
FOR
THE
EXAMINATION
OF
THE
PROPERTIES
AND
CHAR-
.
ACTERISTICS
A data
model is the classical vehicle by which organizations begin to make sense of
their data. The worth of a data model in the systems development process
is seldom questioned in today's sophisticated world of data management
and development.
OF
THE
DIFFERENT
DATA
TYPES
IS
THE
DATA
MODEL
A data model has the following characteristics:
•
It provides a paradigm for systematization.
The paradigm typically or-
ganizes data in subject areas, entities, and tables of data, all of which
satisfy an organization's collective processing requirements.
•
It is a means of identifying commonality of data across applications.
Typically, subject areas such as customer, policy, account, and prod-
uct apply across multiple applications.
•
It is a blueprint for the organization of details at all levels.
An orderly
and rigorous transformation occurs in the structure of data from the
subject area, the high level, to the low-level data model.
•
It is central to the relationship between primitive and derived data.
Knowing how to identify derived data, relate it back to its primitive
source, and then eliminate it from the data model is crucial to the
ability to build and implement a data model in a finite time period.
THE INTERNAL AND EXTERNAL DATA MODELS
In most cases the result of the data modeling exercise is a model of the
customer (or external) interaction with the organization. Banks, insurance
companies, retailers, and public utilities usually focus their data model on
the organization as it interacts with its external environment. Such a data
model is called an external data model because it is developed to facilitate
understanding of the external forces acting on (and interacting with) the
organization.
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