Text File

Aucbvax.2321 fa.works utzoo!duke!decvax!ucbvax!works Thu Jul 16 20:14:48 1981 Re: Making paper go away >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

----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen <jgoerzen@complete.org> of http://communication.ucsd.edu/A-News/

This Usenet Oldnews Archive article may be copied and distributed freely, provided:

1. There is no money collected for the text(s) of the articles.

2. The following notice remains appended to each copy:

The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.