Building the Data Warehouse

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model. As such, there is order and discipline to the design and structuring of the data warehouse. The input to the data warehouse conforms to design specifications of an application that was written a long time ago.

The business conditions behind the application have probably changed 10 times since the application was originally written. Much undocumented maintenance was done to the application code. In addition, the application probably had no integration requirements to fit with other applications. All of these mismatches must be accounted for in the design and building of the data warehouse.

■    The data warehouse reflects the historical need for information, while the operational environment focuses on the immediate, current need for information. This means that an element of time may need to be added as the data moves from the operational environment to the data warehouse environment.

■    The data warehouse addresses the informational needs of the corporation, while the operational environment addresses the up-to-the-second clerical needs of the corporation.

■    Transmission of the newly created output file that will go into the data warehouse must be accounted for. In some cases, this is very easy to do; in other cases, it is not simple at all, especially when operating systems are crossed. Another issue is the location where the transformation will take place. Will the transformation take place on the machine hosting the operational environment? Or will raw data be transmitted and the transformation take place on the machine hosting the data warehouse?

And there is more. This list is merely a sampling of the complexities facing the

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