Database Reference
In-Depth Information
Figure 24-2.
Constructing a Data Warehouse
24.3.4 Twelve Rules That Govern a Data Warehousing
Data warehouse was first introduced by William Inmon in the 1990s; he still operates
as an expert in the field (see [Inmon, 2002] and [Inmon, 2007]). Like E.F. Codd and
C. J. Date of the relational model, Inmon introduced twelve rules for governing data
warehouses. These rules aptly summarize the previously mentioned characteristics of the
data warehouse. Many of these rules have been subsumed in the foregoing discussions.
Nonetheless, for emphasis, they are paraphrased below:
1.
Separation:
The data warehouse and operational database
environments should be separated.
2.
Integration:
The data warehouse data are integrated from
various operational sources.
3.
Time Horizon:
The data warehouse typically contains
historical data with an extended time horizon. This is in
contrast to a significantly shorter time horizon for the
operational databases that may be used as sources for the
data warehouse.
4.
Nature of Data:
The data in a data warehouse represent
snapshot captures (from operational data sources) at specific
points in time.
5.
Orientation:
The data contained in the warehouse are
subject-oriented.
