It is good to have clarity on how WHATWG is working. Thankyou! Sounds like an HTML5 style treatment of the problem.<p>I&#x27;m not clear though why the effective starting point is the <i>superset</i> of all variants currently implemented by one of the involved parties. Given that the extant standards are quite strict, couldn&#x27;t an argument be made that the &quot;burden of proof&quot; would be on why these needed to be extended, on a case by case basis?<p>Regardless of the particular agreements reached, an up-to-date standard will certainly benefit everyone; it seems like it would be an excellent outcome if the standard came with a reference implementation too :-)