MDX extracts multidimensional
views of data. A
tuple is a slice of data
from a cube. It is a selection of members (or cells) across dimensions
in a cube. It can also be viewed as a cross-section or vector of member
data in a cube. A tuple can be composed of member(s) from one or more
dimensions. However, a tuple cannot be composed of more than one
member from the same dimension.
Sets are collections of tuples. The order of tuples
in a set is important when querying cube data and is known as
dimensionality. It is important to note that the
order of the dimension members in every tuple must be the same. For
example, if your first tuple is (time_dimension_member, geography_dimension_member),
then every other tuple in that set must also have two members in it,
the first from the time dimension and the second from the geography
dimension.