Set difference and intersection
These operators were introduced in XPath 2.0.
The expression E1 except E2 selects all nodes that are in E1
         unless they are also in E2. Both expressions must return sequences of nodes.
         The results are returned in document order. For example, @* except @note
         returns all attributes except the note attribute.
The expression E1 intersect E2 selects all nodes that are in both
            E1 and E2. Both expressions must return sequences of nodes.
         The results are returned in document order. For example, preceding::fig intersect
            ancestor::chapter//fig returns all preceding fig elements within the
         current chapter.