🚀 go-pugleaf

>From Joe.Newcomer@CMU-10A Thu Jul 16 19:50:18 1981
One of the main problems in dealing with structured files is that
most operating systems give you "the files" and "the user space"
and you're on your own to figure out what to do with the files.
In Hydra, it was possible to define the text string transformation
of a file as part of the "subfile" type description.  No matter
how peculiar the internal representation of the file might be,
the interface it provided to the outside world was a sequential
"flat" file suitable as input to a compiler or lister.  Of course,
there were other interfaces which were presented; internally, the
editor for that file type was powerful enough to manipulate the
full representation.  One could also have a "display" interface
by which illustrations were made visible on a CRT, or a "printer"
interface by which the file was presented in a form suitable for
printing (e.g., a Press file format would have been possible).
This is necessarily a simplified view, and we didn't begin to
explore all the problems, but the really important idea is that
at the basic interface, an ordinary program could NOT get at the
bits of the file.  Only the bits presented by the file interface.
This abstraction is critical in protecting users from file repre-
sentations, and I consider any file system which does not support
at least this form abstraction to now be hopelessly behind the
state of the art.

I hope to do some more research in this area in the next few
years.  The Hydra idea may NOT be the best, or even close to
right, but it is a whole lot better than any conventional file
system.

(In Unix, it is possible to use pipes to provide the transfor-
 mation; a filter converts a complex file to a sequential byte
 stream.  Alas, Unix does not provide the protection necessary
 to keep any random program from trashing the file by THINKING
 it is a sequential byte stream file.  Nonetheless, their heart
 is in the right place.  This is one of the reasons I think
 pipes are a winning concept).

(The message based operating system for Spice, called Accent,
 makes it possible to build systems with this style of
 interaction).

			joe