Hierarchy values in a cube have both a caption and key. The key will always be unique, but the caption can be the same as for another hierarchy value. The key can be used for identifying a value. When you visualize data from an in-database cube in Spotfire, you may encounter cases where you cannot separate multiple instances of a value from each other (for example, when there are more than one city in the world with the same name (i.e., caption), like the case with Paris, France and Paris, Texas) in a visualization. In that case, you probably want to match values based on the keys, rather than on the values themselves. This is done by selecting the KeyOf method on the matching column of the cube directly.