W3C home > Mailing lists > Public > ietf-http-wg-old@w3.org > January to April 1998

Issue: warning header should be general header, not response header

From: Henrik Frystyk Nielsen <frystyk@w3.org>
Date: Sat, 11 Apr 1998 11:40:31 +0900
Message-Id: <3.0.5.32.19980411114031.007f6b30@localhost>
To: http-wg@cuckoo.hpl.hp.com
Cc: jg@w3.org

Currently the Warning header field is a Response header field:

	14.46 Warning

	The Warning response-header field is used to carry
	additional information about the status of a response
	which may not be reflected by the response status code.
	This information is typically, though not exclusively,
	used to warn about a possible lack of semantic transparency
	from caching operations.

However, in section 13.1.2, it is said that 

	A proxy MUST NOT modify or add any of the following fields
	in a response that contains the no-transform Cache-Control
	directive, or in any request:

		o Content-Encoding
		o Content-Range
		o Content-Type

	A non-transparent proxy MAY modify or add these fields in
	a response that does not include no-transform, but if it
	does so, it MUST add a Warning 114 (Transformation applied)
	if one does not already appear in the response.

The Warning header field must be a general header field to be able to
indicate that a message in a PUT has been modified. This can for example be
used to support advanced image processing in the proxy which is not
available in the client doing the PUT. I admit that the above wording is
quite confusing. I would say:

	A proxy MUST NOT modify or add any of the following fields
	in a message that contains the no-transform Cache-Control
	directive:

		o Content-Encoding
		o Content-Range
		o Content-Type

	A non-transparent proxy MAY modify or add these fields to
	a message that does not include no-transform, but if it
	does so, if not already present, it MUST add a Warning 114
	(Transformation applied).

This would also make it a lot easier to use the Warining header field by
Mandatory, for example.

Henrik
--
Henrik Frystyk Nielsen,
World Wide Web Consortium
http://www.w3.org/People/Frystyk
Received on Saturday, 11 April 1998 01:42:16 EDT

This archive was generated by hypermail pre-2.1.9 : Wednesday, 24 September 2003 06:33:14 EDT