Building the Data Warehouse

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meta data


data


warehouse


classification(s) index words purge date


physical location reference length


related references


Figure 8.3 Meta data takes on a new role in the face of external and unstructured data.


unstructured


data



external


data


meta data


Figure 8.4 Another nice feature of external data and meta data is the ability to create a tailored notification file.


Storing External/Unstructured Data


External data and unstructured data can actually be stored in the data warehouse if it is convenient and cost-effective to do so. But in many cases it will not be possible or economical to store all external data in the data warehouse. Instead, an entry is made in the meta data of the warehouse describing where the actual body of external data can be found. The external data is then stored elsewhere, where it is convenient, as shown in Figure 8.5. External data may be stored in a filing cabinet, on fiche, on magnetic tape, and so on.


However it is done, storing external data and unstructured data requires considerable resources. By associating external data and unstructured data with a data warehouse, the external data and the unstructured data become available for all parts of the organization, such as finance, marketing, accounting, sales, engineering, and so forth. The implication is that once the data is captured and managed centrally, the organization has to undergo the expense of dealing with such data only once. But when external data and unstructured data is not associated with a data warehouse, then there is the very real chance that different

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