From: Anthony Martin
wherein they state the following:
A virtual file system, from the viewpoint of application programs on a
computer, models the file system functions of other computers. This is
done in the same way as with virtual terminals, a virtual file system
consists of a UPP having virtual files (VF), and a UCP which executes
virtual file system protocols.
I'd be interested if you find anything earlier.
MLDEV on ITS would, I think, fit under that description.
I don't know if there's a paper on it; it's mid-70's.
Noel