r describing its own syntax 
(and the syntax of other languages).

Ive been working on the sorted extension but as far as I know nobody 
has been seriously working on the meta-extension.

The sorted extension provides no actual logical expressivity beyond 
the core; it only 'builds in' some of that expressivity into the 
syntax, which many people find convenient. The meta-extension will 
need a fully fledged mechanism for quasi-quotation and a 
truth-predicate, at the very least, and probably some extra inf