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

Tony Sanders (
Thu, 27 Oct 1994 14:29:47 +0100

Jim Davis writes:
> 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
Most of the servers support format negotiation in some form or another.
That's why clients send accept headers and all that other stuff.

> 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.
Not needed for the purpose stated above. URC might do other things
but you don't need them to do basic format negotiation.

> 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.
See for my (old)
proposed solution to that. Also the HTTP spec has some of this stuff
in it as part of the Accept headers.

> 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.
One way or another the user has to be able to indicate they want a specific
format. Whether it be they just say they want PostScript or they tell
the client they want to print it (on their PostScript printer). Either
way the user is making the choice.