Data Warehouse
As per Bill Inmon "A warehouse
is a Historical, subject-oriented, integrated, time-variant
and non-volatile collection of data in support of management's decision
making process".
By Historical we mean, the
data is continuously collected from sources and loaded in the warehouse. The
previously loaded data is not deleted for long period of time. This results in
building historical data in the warehouse.
By Subject Oriented we mean
data grouped into a particular business area instead of the business as a
whole.
By Integrated we mean,
collecting and merging data from various sources. These sources could be
disparate in nature.
By Time-variant we mean that
all data in the data warehouse is identified with a particular time period.
By Non-volatile we mean, data
that is loaded in the warehouse is based on business transactions in the past,
hence it is not expected to change over time.
Data Warehousing
(DWH)
Data warehousing is the vast field
that includes the processes and methodologies involved in the
creating, populating, querying and maintaining a data warehouse. The objective
of DWH is to help users make better business decisions.
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