Re: Format Negociation in Practice [Was: Versioning HTML at the server]

Jim Davis (
Wed, 26 Oct 1994 00:35:13 +0100

Date: Tue, 25 Oct 1994 15:32:23 +0100
From: Tony Sanders <>

"Daniel W. Connolly" writes:
> Format negociation is this nifty idea in theory, but in practice, we see:
> "Click _here_ for postscript, _here_ for text..."

The main missing feature I think is that clients don't currently have any
way to specify what format you want. It would also be extremely helpful
if clients had some way to ask the server what formats it is able to
provide for a given document. This could be done with HEAD by adding a
new object header:
Formats: text/plain,text/html,application/postscript
This is just off the cuff.

Close, but not quite. A single URL is (almost certainly) in exactly
one format . (Though one could imagine a smart server returning
different datatypes depending on information passed in the Accept
field). What you want, I think, is something more like a URC. You
send a URN, and the server tells you what formats it is available in.

This, by the way, is just what Dienst (the technical report server
developed by Carl Lagoze and myself) does. For a demo see

We have submitted an Internet Draft for the Dienst protocol and
would be grateful for any criticism.

It would be nice if the client could also tell the server something
about its display capabilities in the negotiation, e.g. if the
client is running on a monochrome display there's no use sending
the greyscale images.

More importantly I think is that we have to make it easy for
users to select the format of their choice.

Or better yet, for their client (which they have pre-programmed) to
select for them.