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RE: Use of extension-header in entity-header

From: Brian Smith <brian@briansmith.org>
Date: Thu, 21 May 2009 13:00:13 -0500
To: "'Julian Reschke'" <julian.reschke@gmx.de>, "'Brian Smith'" <brian@briansmith.org>
Cc: "'Bjoern Hoehrmann'" <derhoermi@gmx.net>, <ietf-http-wg@w3.org>
Message-ID: <000301c9da3e$00baa7f0$022ff7d0$@org>
Julian Reschke wrote:
> As far as I can tell, this is a left-over from RFC2616 that we're
> planning to address later on. The ABNF as currently written references
> all the micro-ABNFs for the individual headers (well, those defined in
> RFC2616).
> 
> What it should do is just define the generic parsing of header lines
> (what is a legal line? If it is legal, what is the header name and what
> is the field value?), and then refer to each "value" ABNF for the
> individual headers (that's why, in draft-05, we already split the
> header ABNFs into "Fieldname" and "Fieldname-v").

That makes a lot of sense. It means there won't be a complete ABNF grammar
for HTTP messages, but it does mean that the specification will match what
implementations actually do.

(See more comments below.)

Julian Reschke wrote:
> Bjoern Hoehrmann wrote:
> > In RFC 2616 and the current drafts the extension-header is used
> > only in the entity-header production, suggesting all headers not
> > defined by it are entity headers, which I don't think is intended.
> > Perhaps it should be referenced in Request and Response as
> > alternative to entity-header instead?
> 
> I think this is on purpose; Roy has pointed out frequently that
> HTTP/1.1 doesn't have an extension point for this.
> 
> Now, should we / can we fix this? Dunno.

If the change you described above is made, then the grammar won't have
separate general-/response-/request-/entity-/extension- productions, so it
won't matter.

- Brian
Received on Thursday, 21 May 2009 18:00:53 GMT

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