Difference between tuple and set in mdx

Question

What is the difference between tuple and set in MDX. How we can distinguish both and when we are using them.

Answer 1

This article describes the terms Member, Tuple and Set in details.

I'll try to explain it in an easy way.

Simply put, a tuple is an atomic slice of data in a dimension and a set is a collection of tuples. For example, you can have a Books dimension with tuples Sherlock Holmes, Tom Sawyer, CLR via C#, Code Complete and Quantum Physics for Dummies.
After that, you can organize these tuples into named sets, like Programming, Fiction and Natural Sciences.

[Books].&[Sherlock Holmes]                          -- Tuple
[Books].&[CLR via C#]                               -- Tuple
{ [Books].&[CLR via C#], [Books].&[Code Complete] } -- Set

There are certain functions in MDX that return sets or tuples, and it's often helpful to know how to convert a tuple to a set and vice versa. For example, the Item(...) function takes a specific tuple from a set. Enclosing multiple tuples in { , , } will create a set with these tuples.

The example I described is pretty partial and doesn't cover the whole theory, but it might give you a good basic understanding of how these concepts work.