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Re: Last-Modified in chunked footer

From: Roy T. Fielding <fielding@kiwi.ics.uci.edu>
Date: Fri, 05 Sep 1997 08:37:44 -0700
To: Klaus Weide <kweide@tezcat.com>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <9709050844.aa13315@paris.ics.uci.edu>
>In a previous exchange in the RE-VERSION thread, IIRC you argued that
>there was no good reason for a 1.1 client to insist on not receiving
>chunked, since the implementation was simple. (please correct me if my
>memory is wrong.)

Simple when compared to the benefits gained by requiring it, yes.
The requirement is that they be able to recognize and parse it.

>If some dynamic services start sending essential
>headers (which the client needs) in footers because it is easier to
>implement, which they would otherwise send before the body, user agent
>implementers will have a good reason to ask "How can I turn this off".
>Or to just not implement 1.1 and stay 1.0.

If a user agent needs a particular header field before the body, then
a dynamic service is not going to send it in the footer.  Yes, it would
be compliant, but there are a lot of things you can do in HTTP that
are compliant and yet will result in garbage on some user agents.

I think it is wrong to list those things and make them non-compliant
because not all user agents are alike, and not all servers are alike
in their knowledge of the capabilities of the particular client to
which they are talking.  HTTP should be capable of transferring
certain kinds of information even if it is sometimes unwise for it
to do so on the open Internet.  In this sense, we need to differentiate
between capabilities of the protocol (what we are defining) and
capabilities of a particular application of the protocol.  The protocol
requirements should not be dependent on the application, when possible.

>Or are 1.1 user agents free to ignore any headers that come "too late",
>would they still be conformant?

I think that would be reasonable, provided that we have a definition
of "too late".

....Roy
Received on Friday, 5 September 1997 08:48:22 EDT

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