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Professional Microsoft® SQL Server® Analysis Services 2008 with MDX by Denny Guang-Yeu Lee, Robert Zare, Sethu Meenakshisundaram, Matt Carroll, Sivakumar Harinath

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1.7. The Unified Dimensional Model

Central to the architecture is the concept of the Unified Dimensional Model (UDM) which, by the way, is unique to this release of the product. UDM, as the name suggests, provides you with a way to encapsulate access to multiple heterogeneous data sources into a single model. In fact, with the UDM, you will be buffered from the difficulties previously presented by multiple data sources. Those difficulties were often associated with cross-data-source calculations and queries — so, do not be daunted by projects with lots of disparate data sources. The UDM can handle it! The UDM itself is more than a multiple data-source cube on steroids; it actually defines the relational schema upon which your cubes and dimensions are built. Think of the UDM as providing you with the best of the OLAP and relational worlds. UDM provides you with the rich metadata needed for analyzing and exploring data along with the functionality like the complex calculations and aggregations of the OLAP world. It supports complex schemas, and is capable of supporting ad-hoc queries that are needed for reporting in the relational world. Unlike the traditional OLAP world that allows you to define a single fact table within a cube, the UDM allows you to have multiple fact tables. The UDM is your friend and helps you have a single model that will support all your business needs. Figure 1-11 shows a UDM within SQL Server Analysis Services 2008 that retrieves data from heterogeneous ...

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