Can Schematron use grammars to test assertions?
Every schema language does not need to handle every kind of constraint equally well. But in the case of Schematron, I sometimes read the comment that grammars are much easier for some kinds of constraints. And that grammars are more declarative and so help building forms and syntax-directed editors. However, it is possible to do grammars in Schematron. I have circled around this several times before (for example when discussing converting XML Schemas to Schematron) because the trouble with grammars is that often don’t give very satisfactory user messages. But after seeing a spate of papers claiming that Schematron was not as good as other schema languages because it could not represent grammars, I think it might be a good idea to put the code up, in case it is not so clear.
