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Re: rev parameter - LC comment on draft-nottingham-http-link-header-07.txt

From: Mark Nottingham <mnot@mnot.net>
Date: Thu, 4 Feb 2010 17:17:58 +1100
Cc: Apps Discuss <discuss@apps.ietf.org>, HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <3FB0E494-EE9C-46F8-A924-2768C730763A@mnot.net>
To: "Julian F. Reschke" <julian.reschke@gmx.de>, Roy Fielding <fielding@gbiv.com>
I think perhaps you need to talk to Roy about that...

At the moment, my intent is to remove 'rev' from the BNF and state how new parameters can be added (either by updating the document, for parameters common to many relation types, or on a per-type / per-application basis). 



On 22/01/2010, at 8:09 PM, Julian Reschke wrote:

>>> Later on, in the section about HTML4 we find (<http://tools.ietf.org/html/draft-nottingham-http-link-header-07#appendix-B>):
>>> 
>>>  HTML4 also has a "rev" parameter for links that allows a link's
>>>  relation to be reversed.  The Link header does not define a
>>>  corresponding "rev" parameter to allow the expression of these links
>>>  in HTTP headers, due to the confusion this mechanism causes as well
>>>  as conflicting interpretations (briefly, some hold that rev reverses
>>>  the direction of the link, while others that it reverses the
>>>  semantics of the relation itself).
>>> 
>>> I have to admit that I'm still not sure what *in practice* the difference between reversing the link direction and reversing the link semantics actually is. (Example?)
>> I can add a brief example for the latter.
> 
> Please.
> 
>>> So my preference would be to actually define the rev parameter consistently with this, and then to discourage it's use due to the other good reasons we heard about that (such as HTML authors typing "rev" instead of "rel").
>> As previous discussed (quite a bit), HTML2 defines REV as having reversed *semantics*, while HTML4 talks about it creating a "reverse link" -- which are very different things. This feels like a rat hole to me (thus my attempts to navigate around it).
> 
> Again, HTML 2 defines it as:
> 
>    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.
> 
> (<http://tools.ietf.org/html/rfc1866#section-5.7.3>)
> 
> That totally sounds like "reverse link" to me. So, I really really think there's less confusion than some people claim.


--
Mark Nottingham     http://www.mnot.net/
Received on Thursday, 4 February 2010 06:18:35 GMT

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