Using Dimension Expressions
You typically use dimension and hierarchy expressions with a function in Multidimensional Expressions (MDX) to return a member, a set, or a tuple.
Dimension Expressions
A dimension expression either contains a dimension identifier or a dimension function.
A dimension identifier appears as Dimension_Name.
Hierarchy Expressions
Similarly, a hierarchy expression contains either a hierarchy identifier or a hierarchy function.
A hierarchy identifier appears as Dimension_Name.Hierarchy_Name.