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Vary and server parsed documents

From: John Franks <john@math.nwu.edu>
Date: Sat, 30 Aug 1997 07:48:27 -0500 (CDT)
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <Pine.SUN.3.96.970830073418.7633A-100000@hopf.math.nwu.edu>
It is common for servers to parse some documents they serve and
create variations based on headers from the request, the IP address
of the request, etc.  Under 1.1 the exact length of the resulting
document is not known in advance so typically "Transfer-encoding: chunked"
will be used.

The Vary header is designed to list the dimensions along which the
response might vary.  Like the length, this might be difficult to
predict in advance, or might change as the document changes.

On the other hand, calculating the proper Vary header as the document
is being parsed would be simple.  

Would it be possible/reasonable to allow the Vary header in the
trailer of a chunked transfer encoding?  This could make many more
things cachable and would also make for many more accurate Vary
headers in non-cachable responses.

UNREALTED QUERY:  Is there a consensus on the spelling of cachable/cacheable?
Both versions are used in draft 08.  Is there an authority we can
appeal to?


John Franks 	Dept of Math. Northwestern University
		john@math.nwu.edu
Received on Saturday, 30 August 1997 05:53:10 EDT

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