Using Set Functions
A set function retrieves a set from a dimension, hierarchy, level, or by traversing the absolute and relative locations of members within these objects, constructing sets in a variety of ways. A set function can also retrieve sets by resolving the string representation of a set.
Set functions, like member functions and tuple functions, are essential to negotiating the multidimensional structures found in Multidimensional Expressions (MDX). Set functions are also essential to obtaining results from MDX queries because set expressions define the axes of an MDX query.