Dimensions implement the user interface UI in a business intelligence BI tool. In a dimensional data warehouse DW/BI system, the textual descriptors of all the data warehouse entities like customer, product, location and time reside in dimension tables. My two previous columns carefully described three major types of dimensions according to how the DW/BI system responds to their slowly changing characteristics. But why all this fuss about dimensions? They are the smallest tables in the data warehouse, and the real “meat” is actually the set of numeric measurements in the fact tables. But that argument misses the point that the DW/BI system is always accessed through the dimensions. The dimensions are the gatekeepers, the entry points, the labels, the groupings, the drill-down paths and, ultimately, the texture of the DW/BI system. The actual content of the dimensions determines what is shown on the screen of a BI tool and what UI gestures are possible. That is why we say that the dimensions implement the UI.