Understanding Unified Dimensional Modeling
The Unified Dimensional Model (UDM) is one of the key features of Analysis Services. In addition to removing the requirement that each dimension's hierarchies (or rollups) must be defined only at time of creation, Microsoft has simplified dimensional modeling by basing all dimensions on attributes. Simply put, each column from the source dimension table is (by default) an attribute for that dimensional item.
A hierarchy in SSAS is a grouping mechanism, and serves two purposes. The first is largely a convenience for end users. This type of hierarchy is called a browse (or navigational) hierarchy. The second type is called a natural hierarchy and will be discussed in greater detail in Chapter 3, “Introducing ...
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