Often, we'll need to create groups of some kind on a dimension either to group long lists of members up into more user-friendly groups, or to group numeric attributes such as Age or measure values into bands or ranges. Analysis Services offers some functionality to help us do this. But as usual, we'll get much more flexibility if we design these groups into the dimension ourselves.
First of all, let's consider why we might want to group members on a large attribute hierarchy. Some dimensions are not only very large—there are a lot of rows in the dimension table—but they are also very flat, so they have very few attributes on them that are related to each other and have very few natural hierarchies. We might have a Customer dimension with millions of individual customers on it, and we might also have City and Country attributes, but even then it might be the case that for a large city, a user might drill down and see hundreds or thousands of customers. In this...