sequence[not(item)]

Assume that the root element, <sequences>, is the context node.

Is that the right way to express the rule?


It's Ok, arguably sequence[empty(item)] is more direct (as it relies
less on the implicit boolean value of a list of items) but it's same
thing really (I tend to use not() as empty() is a newfangled xpath2
addition)

every $element in $set//element satisfies exists(sequence[(item =
$element) and not(item[2])])

looks OK to me, an alternative might be

not($set/element[not(.=current()/sequence[not(item[2])]/item)])

which is also xslt1 1 again as it happens.

David