Building the Data Warehouse

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Design review is as applicable to the data warehouse environment as it is to the operational environment, with a few provisos.


One proviso is that systems are developed in the data warehouse environment in an iterative manner, where the requirements are discovered as a part of the development process. The classical operational environment is built under the well-defined system development life cycle (SDLC). Systems in the data warehouse environment are not built under the SDLC. Other differences between the development process in the operational environment and the data warehouse environment are the following:


■■ Development in the operational environment is done one application at a time. Systems for the data warehouse environment are built a subject area at a time.


■■ In the operational environment, there is a firm set of requirements that form the basis of operational design and development. In the data warehouse environment, there is seldom a firm understanding of processing requirements at the outset of DSS development.


■■ In the operational environment, transaction response time is a major and burning issue. In the data warehouse environment, transaction response time had better not be an issue.


■    In the operational environment, the input from systems usually comes from sources external to the organization, most often from interaction with outside agencies. In the data warehouse environment, it usually comes from systems inside the organization where data is integrated from a wide variety of existing sources.


■    In the operational environment, data is nearly all current valued (i.e., data is accurate as of the moment of use). In the data warehouse environment, data is time variant (i.e., data is relevant to some one moment in time).

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