A simpler XML approach is to use elements named root-node, left-node, and right-node.  That reduces the number of levels in the tree by half.

In addition, I don't know of any parsers that use recursion in the language to support recursion in the tree; the nesting is normally stored as an array of element objects, either fixed (in which case you get an error) or growable.  Such a structure can of course be traversed in XSLT, but not with native traversal mechanisms..  Your flat representation doesn't gain you much, then.

John Cowan          http://vrici.lojban.org/~cowan        cowan@c...
Cash registers don't really add and subtract;
        they only grind their gears.
But then they don't really grind their gears, either;
        they only obey the laws of physics.  --Unknown