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

[Julian Reschke <[e-mail]>]

Mark Nottingham wrote:
> ...
> I'm happy to remove it from the BNF if that doesn't disturb the very delicate consensus we have on this topic. Comments from others?
> ...

Optimally, it gets defined. Otherwise it should be clear through which 
path somebody else can define it.

>> Speaking of which, how do I define an extension? Standards Track RFC updating this one, as there is no registry?
> 
> If you like. Practically speaking, I think many extensions will be used without such registration, as they'll be specific to the format and/or application in use -- which I think is just fine.
> 
>> 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.

Best regards, Julian