7) Schematron can handle validating content models with the same element names in more than one position in a content model using regular expression string matching, but this gives less useful messages.

8) A complex content model was actually often the sign that grammars were not elegant to express the constraints.  Sometimes handwritten assertions could do a much better job at capturing the real constraint, rather than a verbose Schematron version of a verbose Content Model version of the constraints!