Chapter 3
Data Warehouse and OLAP
Technology: An Overview
Data
warehousing provides architectures and tools for business executives to
systematically
organize, understand, and use their data to make strategic decisions.
DEFIITION
:According to William H. Inmon, a
leading architect in the construction of data
warehouse systems, “A data warehouse is
a subject-oriented, integrated, time-variant, and
nonvolatile collection of data in
support of management’s decision making process”.
The four keywords,
subject-oriented, integrated, time-variant, and nonvolatile,
distinguish data warehouses from other
data repository systems, such as relational
database systems, transaction processing
systems, and file systems.
Subject-oriented:
A data warehouse is organized around major subjects, such as cus-
tomer, supplier, product, and
sales.Hence, data warehouses typically
provide a simple and concise view around
particular subject issues by excluding data
that are not useful in the decision
support process.
Integrated:
A data warehouse is usually constructed by integrating multiple heteroge-
neous sources, such as relational
databases, flat files, and on-line transaction records.
Time-variant:
Data are stored to provide information from a historical perspective
(e.g., the past 5–10 years).
Nonvolatile:
A data warehouse is always a physically separate store of data trans-
formed from the application data found
in the operational environment.It usually requires
only two operations in dataaccessing:
initial loading of data and access of data.
A data warehouse
is also oftenviewed as an architecture, constructed by integrating
data from multiple heterogeneoussources
to support structured and/or ad hoc queries,
analytical reporting, and
decisionmaking.
Many Organizations use the information from data warehouses to
support business
decision-making
activities, including :
(1) increasing
customer focus, which includes the analysis of customer buying
(2) repositioning products and managing
product portfolios by comparing the
performance of
sales by quarter, by year, and by geographic regions in order to fine-
tune production
strategies;
(3) analyzing
operations and looking for sources of profit;and
(4) managing the
customer relationships, making environmental corrections, and
managing the
cost of corporate assets.