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Re: COMMENT: LAST CALL comment

From: David W. Morris <dwm@xpasc.com>
Date: Wed, 4 Jun 1997 10:58:28 -0700 (PDT)
To: Ross Patterson <Ross_Patterson@ns.reston.vmd.sterling.com>
Cc: http-wg@cuckoo.hpl.hp.com
Message-Id: <Pine.GSO.3.96.970604105154.12205B-100000@shell1.aimnet.com>


On Wed, 4 Jun 1997, Ross Patterson wrote:

> http-wg@cuckoo.hpl.hp.com writes:
> 
> >Larry Masinter:
> There's clearly a contradiction between the BNF and the text, and as I
> can find no references in the RFC to "quoted-pair", I'm inclined to
> agree with Roy Fielding that the BNF is in error.  The change in stance
> between HTTP 1.0 and 1.1 on backslash-enquoting is quite clear in the
> text, and the BNF for "quoted-pair" is new in HTTP 1.1.  Thank goodness
> comments are only legal within Server, User-Agent, and Via fields!
> 
> Accepting Roy's assertion does, however, open one other area of concern:
> use of the "quoted-string" BNF by other parts of the grammar.  For
> example, entity tags are defined as "opaque-tag", and opaque-tag is
> defined as "quoted-string".  Therefore quoted-pairs must be legal within
> opaque-tags.  So what is the proper meaning of "opaque" - do we dequote
> quoted-pairs within opaque-tags before comparison or not?  The former
> changes them more into "translucent-tag"s, the latter risks

THere is the syntatic quoted string and there is the value represented
by the quoted string. I assert that the value and not the transfer
mechanism is opaque. Before comparison of a quoted string, it must
be transformed into its value. That is, remove the transfer encoding.

> mis-comparing tags that would be equal after dequoting (e.g., "a \b c"
> vs.  "a b c").
> 
> Interestingly, allowing quoted-pairs withing quoted-strings would bring
> HTTP's definition of media-type parameters back in line with MIME's.
> MIME relies on the RFC 822 definintion of quoted-string, which allows
> quoted-pairs, and "value" is defined in both HTTP and MIME as "token |
> quoted-string".

In the world of computer science, the principal of no suprises would
dictate that the correct 'design' is quoted-pairs are supported.

This may be a case where the minimal risk of HTTP/1.0 breakage should bow
to the greater common good. My intuition is that there is at least as
good a chance that the implementors of HTTP/1.0 servers and clients
have really implemented full support for quoted pairs as restricted 
support. Full support is easier and follows other examples such as
the C programming language.

Dave Morris
Received on Wednesday, 4 June 1997 12:57:42 EDT

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