Epischema Article on XML.com

Adding a second Relax NG schema in the way you'd add a Schematron schema 
is an (in my view) nice approach to constraining a base schema.
It is orthogonal like Schematron: You don't need to know or modify the 
building blocks that the base schema provides.
Unlike Schematron rules, the additional Relax NG schema may be used by 
XML editors for content completion.
Those of you who listened to this year's XML Prague presentation [1,2] 
about adding a Docbook-like grammar to TEI divs already know the 
concept. In a recent article on XML.com [3], I've applied this approach 
to HTML, using the HTML-first publishing workflow that Dave Cramer 
described [4] as an example.
I've called this approach, that to my surprise (and admittedly modest 
knowledge) was hitherto unheard of, "epischema" (epi = on top of).
Please note that I'm not advocating against the use of Schematron; on 
the contrary. It's just that there's an alternative way to express a 
certain class of constraints (grammatical ones), and this alternative 
provides specific, context-dependent content completion suggestions as a 
side effect.
Looking forward to receiving your comments.

-Gerrit

[1] 
http://archive.xmlprague.cz/2017/files/presentations/epischema/index.html
[2] https://youtu.be/BOHtdnQEokQ?list=PLQpqh98e9RgUcEmbXmI6RolisQaIRw9dm
[3] https://www.xml.com/articles/2017/04/29/epischemas/
[4] https://www.xml.com/articles/2017/02/20/beyond-xml-making-books-html/