Building the Data Warehouse

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A series of problems arise when the groups overlap. The first problem is cost— in particular, the cost of storage and processing. The volumes of data that are found at the current detailed level are such that any amount of redundancy must be questioned, much less wholesale redundancy. The cost of processing the detail is likewise a major issue.

The second, more insidious issue is the introduction of the spider web into the DSS environment. With massive amounts of redundant detailed data, it is almost axiomatic that misinterpretation of data caused by redundancy will occur, where there is no effective reconcilability. Creating large amounts of

development group A

Figure 6.31 Different development groups that are developing the current level of detail for the data warehouse.

development group C

redundant detailed data is a very undesirable condition for the detailed level of data in the data warehouse and defeats its purpose. If multiple development groups will be doing concurrent design and population in the current level of detail, great care must be taken to ensure that no redundant detailed data is created.

To ensure that no redundant data is developed, it is necessary to create a data model that reflects the common detailed data. Figure 6.32 shows that multiple development groups have combined their interests to create a common data model. In addition to the currently active development groups, other groups that will have future requirements but who are not currently in a development mode may also contribute their requirements. (Of course, if a group knows it will have future requirements but is unable to articulate them, then those requirements cannot be factored into the common detailed data model.) The common detailed data model reflects the collective need among the different groups for detailed data in the data warehouse.

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