tailieunhanh - Building the Data Warehouse Third Edition phần 7

Chi tiết dự phòng dữ liệu là một điều kiện rất không mong muốn cho các cấp độ chi tiết của dữ liệu trong kho dữ liệu và đánh bại mục đích của nó. Nếu nhiều nhóm phát triển Will Be làm thiết kế đồng thời và dân số ở mức hiện tại của chi tiết, lớn chăm sóc phải được thực hiện để đảm bảo dữ liệu Đó không phải là chi tiết dư thừa tạo ra. | Uttama Reddy L236 CHAPTER 6 development group A development group B development group E development group D development group C Figure Different development groups that are developing the current level of detail for the data warehouse. redundant detailed data is a very undesirable condition for the detailed level of data in the data warehouse and defeats its purpose. If multiple development groups will be doing concurrent design and population in the current level of detail great care must be taken to ensure that no redundant detailed data is created. To ensure that no redundant data is developed it is necessary to create a data model that reflects the common detailed data. Figure shows that multiple development groups have combined their interests to create a common data model. In addition to the currently active development groups other groups that will have future requirements but who are not currently in a development mode may also contribute their requirements. Of course if a group knows it will have future requirements but is unable to articulate them then those requirements cannot be factored into the common detailed data model. The common detailed data model reflects the collective need among the different groups for detailed data in the data warehouse. The data model forms the basis of the design for the data warehouse. Figure shows that the data model will be broken up into many tables as design progresses each of which physically becomes part of the warehouse. Because the data model is broken into multiple physical tables at the moment of implementation the development process for the data warehouse can proceed in an iterative manner. There is no need to build all of the tables at once. In fact a good reason to build only a few tables at a time is so that the end user Uttama Reddy The Distributed Data Warehouse 237 data unique to development group A data unique to development group D data common to development groups A B C D data unique to