> It is not correct, regardless of how many times it is said.
I'd agree with this (even though you posted it to contradict a
statement of mine:-)
I'd also agree with my original statement. Terminology isn't always
consistently applied.
> A set can be ordered or unordered.
A set as defined in most set theories doesn't have any concept of order.
Now you can of course have a set with an order (or often a set with a
partial order: `poset') this formally is a pair consisting of a set and
an ordering relation. However the common name for the pair is "ordered
set" so you end up with the fact that it's a reasonable position
to use the word "set" in either way. You just need to define your terms.
And in the case of XSL I'd claim that "set" is used in the way I
indicated. Consider sets of integers. The set {1,2,3} and {3,2,1}
are the same set. But the ordered sets
( {1,2,3} , < ) and ( {1,2,3} , > )
ie the set ordered by less-than and greater-than relations, respectively
are different ordered sets.
When talking about document order or reverse document order in XSLT
this is always a relation that is _applied_ to a node set, it is not an
intrinsic property of the node set itself, in the way that the order is
an intrinsic propoerty of an ordered set.
It is not possible to have two different node sets with the same
underlying collection of nodes, but different orderings as would be the
case if ordered sets were your underlying model.
David
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