A month later (March 1999), in reply to a different thread I posted:
Wouldn't that be great? The UNIX pipe model has suffered from not having a standard structured format, as has the /proc file system. Not to mention what this could do to an OS like Plan9 where "everything is a file" and textual formats abound...
This is pretty much what I was suggesting a little while ago on this list (in the same breath as überdocument). I'm still trying to find the time to work a bit more on it. I certainly have a lot of ideas about it so if others are interested in helping with implementation, I'd love them to drop me an email. My idea involves a layer on top of the operating system that treats the operating system as one big XML document (hence the phase "überdocument shell" which I used at the time).
I'm thinking of calling it "Plan X" which both includes the mandatory "X" for association with XML and suggests, via roman numeral, a continuation of the thinking of Plan 9.