The life cycle of a data warehouse and its ETL processes (Vassiliadis,
Simitsis, & Skiadopoulos, 2002a)
22 Simitsis, Vassiliadis, Skiadopoulos, & Sellis
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of specific physical structures in the warehouse (e.g., indexes) and environmentspecific
execution parameters for the operational processes. We call this stage tuning
and its deliverable is the physical model of the environment. In a fourth stage,
software construction, the software is constructed, tested, evaluated, and a first
version of the warehouse is deployed. This process is guided through specific software
metrics. Then, the cycle starts again, since data sources, user requirements,
and the data warehouse state are under continuous evolution. An extra feature that
comes into the scene after the deployment of the warehouse is the administration
task, which also needs specific metrics for the maintenance and monitoring of the
data warehouse. Consequently, in order to achieve our goal we have to deal with
the phases of the life cycle of a data warehouse.
??? Conceptual.model:.A conceptual model for ETL processes deals with the
earliest stages of the data warehouse design. During this period, the data warehouse
designer is concerned with two tasks which are practically executed in
parallel: (a) the collection of requirements from the part of the users, and (b)
the analysis of the structure and content of the existing data sources and their
intentional mapping to the common data warehouse model.
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