Re: misconceptions about MIME [long]

Larry Masinter (masinter@parc.xerox.com)
Tue, 27 Oct 1992 14:38:18 PST 

To: NED@sigurd.innosoft.com
Cc: nsb@thumper.bellcore.com, wais-talk@quake.think.com,
In-Reply-To: Ned Freed's message of Thu, 22 Oct 1992 22:39:33 -0700 <01GQ9KR9LCZ09D4EDD@SIGURD.INNOSOFT.COM>
Subject: Re: misconceptions about MIME [long]
From: Larry Masinter <masinter@parc.xerox.com>
Message-Id: <92Oct27.143829pst.101795@poplar.parc.xerox.com>
Date: 	Tue, 27 Oct 1992 14:38:18 PST

I no longer know what forum to address this to, I suppose we've been
asked to remove the discussion from 'gopher@boombox.micro.umn.edu'.

The arguments that in-band designation of document format is better
than out-of-band information may apply in the electronic mail
scenarios, where there is a single sender, multiple recipients, and
the recipient has no control over what the sender might send.

Instead, imagine, if you would, another scenario, of a WAIS or Web or
anonymous FTP archive, which wishes to make available the latest
version of the MIME specification. Let us suppose, in addition, that
the publishing service has three different representations of the
document, one marked "MIME rich-text", one marked "postscript", and
one NetFax.  Furthermore, let us suppose (as has been proposed) that
the document types are marked by their MIME Content-type header
designation.

If I wish to retrieve the document, say to view it, I might want to
choose the available representation that is most appropriate for my
purpose. Imagine my dismay to retrieve a 50 megabyte postscript file
from an anonymous FTP archive, only to discover that it is in the
newly announced Postscript level 4 format, or to try to edit it only
to discover that it is in the (upwardly compatible but not parsable by
my client) version 44 of Rich Text. In each case, the appropriateness
of alternate sources and representations of a document would depend on
information that is currently only available in-band.

I believe that MIME was developed in the context of electronic mail,
but that the usage patterns in space and time of archives, database
services and the like require more careful attention (a) to
out-of-band information about format versions, so that you might know,
before you retrieve a representation, whether you have the capability
of coping with it, and (b) some restriction on those formats which
might otherwise be uncontrollable.

Finally, as much as I've tried to resist, I'll characterize your
description of my response as 'repeated failure on your part to read
the words I was writing' as 'inflammatory hogwash'.