It is better to log the string length from root to the beginning of each particular node, and then use that number to rank the elements from Top to Bottom. In fact, that is what I want to do. What be your recommendation to do that?

I'm sorry, I really have very little idea what you are trying to achieve.

If you want to sort the paths such that the nodes they reference are in
document order, then I don't think you have enough information. You need to
retrieve the actual nodes and sort them into document order

Michael Kay
http://www.saxonica.com/