Consider creating a construct for actions that iterates over a nodeset.
As with the @while attribute, an attribute such as @for, @foreach or @iterate could be added to perform the action to which the attribute is attached once for each node of the nodeset.
The specification should identify what happens if the contained action sequence deletes nodes from the nodeset being iterated. The speciication should also identify what should happens if nodes are inserted into the nodeset. Finally, the specification should identify what happens if the action sequence sets a value that is consumed by a predicate in the nodeset, thereby indirectly adding to or deleting from the nodeset.
See eXforms for some inspiration: http://www.exforms.org/conditionals.html#id4484032
Erik's note: w/ XPath 2.0, iterate over a sequence rather than nodeset.