May be that ConTeXt is not a 'context free language' ;-) than it will be difficult to express something in a BNF grammar http://en.wikipedia.org/wiki/Backus-Naur_form.
hmm. Context is a macro package in TeX language which is Turing Complete.
But if (ConTeXt == formal_language), it should be possible to develop TEXT, NUMBER, DIMENSION, REFERENCE, etc and also to add examples for "[optional user data]".
hmm I'm not sure that ConTeXt == TeX (but it seems YES) , I'm nor sure that TeX is a context free language too, in the sense that I never see a BNF grammar of TeX . (chap.24-26 of the Texbook are embryos of a grammar, but they are not usable
On Wed, 29 Apr 2009 17:55:05 +0200
luigi scarso
I suspect that TeX is not a cfl .
Anyway, lpeg can make the thing easier
-- luigi
I think that something user-friendly could be do in a cooperative wiki (in the between, i found http://texshow.contextgarden.net/) beginning with CONTEXT_SOURCE ::= PREAMBLE "\starttext" TEXT "\stoptext" | CONTEXT_SOURCE TEXT ::= STARTSTOPS | SETUPS | DEFINES | OTHERS [ TEXT and so on.