Hi Ned,
I've been following this discussion for a while now, and while it pains me to object to something that would lessen my own workload, I find that I have to agree with Keith about this. The stability problems associated with DNS names are just too great. [...] Given the huge amount of damage that's been inflicted on the world by badly designed media types, I am forced to see further reduction of the barriers as a reckless step in the wrong direction.
I agree these are the biggest -- and serious -- concerns with the proposal. However, the status quo doesn't seem to be working too well; rather than discouraging frivolous or poorly-considered media types, it encourages people into the "x-" space. This is borne out when you examine mime.types files and Web browser configurations; deployed software and formats are ignoring the process quite freely. The other effect is that it encourages people to avoid media types altogether, so that formats don't have well-known identifiers, or if they do, ones that aren't usable in current systems like MIME or the Web (QNames in WSDL come to mind especially). A DNS-based type does indeed have a chance of the authority changing, but I believe this possibility is preferable to the lack of a usable identifier. So, I'd put forth that the current system doesn't discourage badly designed media types (or formats); every incentive is for people to use the "x-" space, though it is officially discouraged, leading to confusion. It does discourage well-designed media types and formats from actually being registered, which hurts software and systems that leverage them. If there's another solution to this, I'm all ears. Cheers, -- Mark Nottingham http://www.mnot.net/