Suggestions for Foreign RelaxNG-based Vocabulary for Foreign Specialization Example

As part of the RNG proposal I need to add an RNG example of foreign specialization.
Since DTD is SVG and XSD is MathML, it seems reasonable to pick a third for RNG.
However, I’m having a hard time coming up with one.
Chemical Markup Language seemed likely but I can only find an XSD schema and there is no ready XSD-to-RNG converter I can find.
Chris suggested the Rule Markup Language but it’s quite large and a bit hard to sort out quickly.
Any other ideas?
Thanks, E.

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Eliot Kimber Senior Solutions Architect "Bringing Strategy, Content, and Technology Together" Main: 512.554.9368 www.reallysi.com www.rsuitecms.com