Building the Data Warehouse

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Yet another major consideration when passing data is the need to manage the volume of data that resides in and passes into the warehouse. Data must be condensed both at the moment of extraction and as it arrives at the warehouse. If condensation is not done, the volume of data in the data warehouse will grow rapidly out of control. Figure 3.6 shows a simple form of data condensation.

Data/Process Models and the Architected Environment

Before attempting to apply conventional database design techniques, the designer must understand the applicability and the limitations of those techniques. Figure 3.7 shows the relationship among the levels of the architecture and the disciplines of process modeling and data modeling. The process model applies only to the operational environment. The data model applies to both the operational environment and the data warehouse environment. Trying to use a process or data model in the wrong place produces nothing but frustration.

Figure 3.6 Condensation of data is a vital factor in the managing of warehouse data.

In general there are two types of models for the information systems environment—data models and process models. Data models are discussed in depth in the following section. For now, we will address process models. A process model typically consists of the following (in whole or in part):

■■ Functional decomposition ■■ Context-level zero diagram ■■ Data flow diagram ■■ Structure chart

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