Re: Mailcap extensions (was Re: Client Compliance)

Chris Adie (
Thu, 1 Sep 1994 12:06:32 +0200

> > > It's never been very clear to me what a server should do if it cannot
> > > present an item in a format the client will accept. Return an error?
> > > Which one?
> >
> > The Windows-NT server from EMWAC tries to do this, but has a few problems
> > when it sees multiple Accept: headers instead of having one huge one. I
> > believe it just returns one of the more generic error codes (401 or
> > something like that).
> Quite understandable, given the lack of clearness on what to do.
> Unfortunately, this makes it impossible for the client to respond
> appropriately (with something like "This document is only available in
> formats I do not understand. Woud you like to download it anyway?", ideally
> enumerating which formats it *is* available in and allowing the user to
> choose one.)
> In the meanwhile, let me guess, it responds with those famous words,
> "The information server either is not accessible or is refusing to serve the
> document to you." :-)

Actually, it responds with satus 400 and a message "The document is
of a type which is not supported by your client".

I hereby propose using a new status code 405 for this

Unsupported Type 405
The object requested has a MIME type which does not correspond to
any of the types which the client indicated it can accept.

Is returning this code going to break any existing browsers?


Chris Adie Phone: +44 31 650 3363
Edinburgh University Computing Service Fax: +44 31 650 6547
University Library, George Square Email:
Edinburgh EH8 9LJ, United Kingdom