att.global/@n is currently defined as have a datatype of
<ref xmlns="http://relaxng.org/ns/structure/1.0" name="data.word"/>
which excludes certain characters ("only letters, digits, punctuation characters, or symbols"),
but is unbounded so can have spaces.
This is silly. Its plain text, and needs a plain <rng:text> datatype. What would it mean to have
multiple values for @n?