Help with multiple deletes

[Martin Probst]

I guess your approach is a bit different than what the spec planned -
their idea was that you'd just want to perform the updates, but not
"witness" the effects.

A different approach would be this:
copy $x := doc("tree.xml")
modify (
       let $node := $x//tree[@ID = 1] /branch[@ID = 2] /branch[@ID =
13] /branch[@ID = 65]
           /branch[@ID = 15] /leaf[@ID = 25]
       let $empty-branches := $x//branch[count(.//leaf except $node) = 0]
       let $empty-trees := $x//tree[count(.//branch except $empty-branches) = 0]
       return delete nodes ($empty-trees, $empty-branches, $node)
)
return $x

There might be more efficient ways to find the nodes that need
pruning, in particular if your implementation would support the
ancestor:: axis, you could walk upwards from $node instead of scanning
the whole tree for the $empty-* variables.

Martin