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Re: Feedback for draft-nottingham-http-link-header-03

From: Yves Lafon <ylafon@w3.org>
Date: Wed, 10 Dec 2008 06:01:15 -0500 (EST)
To: Julian Reschke <julian.reschke@gmx.de>
cc: Mark Nottingham <mnot@mnot.net>, "Roy T. Fielding" <fielding@gbiv.com>, HTTP Working Group <ietf-http-wg@w3.org>
Message-ID: <Pine.LNX.4.64.0812100553470.10171@ubzre.j3.bet>

On Wed, 10 Dec 2008, Julian Reschke wrote:

>
> Mark Nottingham wrote:
>> ...
>>       <t>HTML4 also has a "rev" parameter for links that allows a link's 
>> relation to be reversed. The Link header
>>         has a "rev" parameter to allow the expression of these links in 
>> HTTP headers, but its use is not encouraged,
>>         due to the confusion this mechanism causes as well as conflicting 
>> interpretations among HTML versions.</t>
>> ...
>
> OK, it seems I'm missing something here. Could somebody explain to me, what 
> the conflicting interpretations are, and which we prefer (and why?)?
>
> HTML2 (<http://tools.ietf.org/html/rfc1866#section-5.7.3>):
>
>    REL
>            The REL attribute gives the relationship(s) described by
>            the hyperlink. The value is a whitespace separated list
>            of relationship names. The semantics of link
>            relationships are not specified in this document.
>
>    REV
>            same as the REL attribute, but the semantics of the
>            relationship are in the reverse direction. A link from A
>            to B with REL="X" expresses the same relationship as a
>            link from B to A with REV="X". An anchor may have both
>            REL and REV attributes.

In that case, it's not a reversed link, but still a normal forward link, 
but it expressed a reversed relationship.
A: link rel="bigger than" B
is the same relation as
B: link rev="smaller than" A

Same relation, but different links (and different authority claiming the 
relationship between both A and B).
In the HTML4 example, it's reverse and forward links, so the links are 
supposed equivalent, so not only the relation is equivalent, but also the 
link.
I prefer far more the "relationship equivalence" as defined in HTML2.

> HTML4 (<http://www.w3.org/TR/html4/struct/links.html#rev-link>):
>
>  12.3.1 Forward and reverse links
>
>  The rel and rev attributes play complementary roles -- the rel
>  attribute specifies a forward link and the rev attribute specifies a
>  reverse link.
>
>  Consider two documents A and B.
>
>    Document A:       <LINK href="docB" rel="foo">
>
>  Has exactly the same meaning as:
>
>    Document B:       <LINK href="docA" rev="foo">
>
>  Both attributes may be specified simultaneously.
>
>
>
> Best regards, Julian
>

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves
Received on Wednesday, 10 December 2008 11:01:24 GMT

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