Building the Data Warehouse

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At first glance it may seem that there is a lot of redundant data between the data warehouse and the ODS. After all, the ODS is fed from the data warehouse. (Note: The ODS being discussed here is a class IV ODS. For a complete description of the other classes of ODS, refer to my book Building the Operational Data Store, Second Edition (Wiley, 1999).

But in truth there is very little overlap of data between the data warehouse and the ODS. The data warehouse contains detailed transaction data, while the ODS contains what can be termed “profile” data. To understand the differences

Web environment

be-tween profile data and detailed transaction data, consider the data seen in Figure 10.5.

The data warehouse contains all sorts of transaction data about past interactions between the customer and the business. Detailed transaction data includes information about the following:

■■ Searches for men’s bicycles ■■ Searches for women’s red bathing suits ■■ Purchases of a women’s blue bathing suits ■■ Searches for Ray-Ban wraparounds

The data warehouse maintains a detailed log, by customer, of the transactional interactions the customer has had with the business, regardless of the source of the interaction. The interaction could have occurred on the Web, through a cat-



data warehouse

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