By long custom in music school, we say that the "melodic minor" has two forms, ascending and descending. But really the minor scale is a variable one whose 6th and 7th degrees are often altered, particularly when ascending. A descending "melodic minor" is just the natural minor scale again.
Hierarchical scale is the use of scale to indicate relative importance. In the royal altar to the hand, the king is at the center because he is the most important followed by his attendants.
