Extra-Grammatical Constraints

  • Exclusions. (High on my list of features for a future version of RELAX NG.)

  • A version attribute on the root element.

  • Enforcing implicit constraints. (In a segmented list, the number of segments in each list item has to be the same as the number of titles specified.)

  • Enforcing referential integrity constraints. (A cross-reference on a footnoteref must point to a footnote.)