2824961_1_data-warehouse-engineering-process.pdf

Fig 3 client conceptual schema level 1 fig 4 client

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Fig. 3. Client Conceptual Schema (level 1) Fig. 4. Client Conceptual Schema (level 2) Fig. 5. Client Conceptual Schema (level 3) 3.7 Test The goal of this workflow is to verify that the implementation works as desired. No new diagrams are created, but previous diagrams (mainly design and imple- mentation diagrams) may be modified according the corrective actions that are taken.
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Fig. 6. Client Physical Schema 3.8 Maintenance Unlike most systems, the DW is never done. The goal of this workflow is to define the refresh and loading processes needed for keeping the DW up to date. This workflow starts when the DW is built and delivered to the final users, but it does not have an end date (it lasts during the life of the DW). During this workflow, the final users can state new requirements, such as new queries, which triggers the beginning of a new iteration (UP is an iterative process) with the Requirements workflow. 3.9 Post-development review This is not a workflow of the development effort, but a review process for im- proving future projects. We look back at the development of the DW, revise the documentation created, and try to identify both opportunities for improvement and major successes that should be taken into account. If we keep track of the time and effort spent on each phase, this information can be useful in estimating time and staff requirements for future projects. 3.10 Top-down or Bottom-up? Nowadays, there are two basic strategies in the building of a DW: the top-down and bottom-up approaches. The top-down approach recommends the construc- tion of a DW first and then the construcion of DMs from the parent DW. The bottom-up approach uses a series of incremental DMs that are finally integrated to build the goal of the DW. However, in almost all projects, the DMs are built rather independently without the construction of an integrated DW, which is indeed viewed no more as a monolithic repository but rather as a collection of DMs.
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Our method also allows both approaches. In the top-down approach, the DW is built first and the data sources are the transactional systems; then, each DM is built independently by using our method, and the DW becomes the only data source for all of them. In the bottom-up approach, the DMs are built first from the transactional systems; then, the DW is built and the data sources are the DMs. 4 Conclusions In this paper, we have presented the Data Warehouse Engineering Process (DWEP), a data warehouse (DW) development process based on the Unified Modeling Lan- guage (UML) and the Unified Process (UP). UP is a generic and stable process that we have instantiated to cover the development of data warehouses. Our main contribution is the definition of several diagrams (techniques) and UML profiles [16,17,18] in order to model DWs more properly. Whereas the different diagrams provide different views or perspectives of a DW, the engineering pro- cess specifies how to develop a DW and ties up all the diagrams together. The main advantages of our approach are:
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