Re: [apps-discuss] Link rel uniqueness

Mark Nottingham <mnot@mnot.net> Sun, 21 October 2012 07:51 UTC

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From: Mark Nottingham <mnot@mnot.net>
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Date: Sun, 21 Oct 2012 18:51:03 +1100
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To: Jan Algermissen <jan.algermissen@nordsc.com>
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Subject: Re: [apps-discuss] Link rel uniqueness
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No. link-value is the syntactic construct of *one* link; see the ABNF. There can be multiple links with the same target; this is just saying that there can only be one "rel" parameter on each link.

Cheers,


On 21/10/2012, at 6:49 PM, Jan Algermissen <jan.algermissen@nordsc.com> wrote:

> 
> On Oct 21, 2012, at 5:52 AM, Mark Nottingham wrote:
> 
>> Hi Jan,
>> 
>> What's the specific requirement you're referring to?
> 
> Section 5.3.:
> 
> "The relation type of a link is conveyed in the "rel" parameter's
>   value.  The "rel" parameter MUST NOT appear more than once in a given
>   link-value; occurrences after the first MUST be ignored by parsers."
> 
> I was unsure what the link-value refers to but from what you write below I understand that it refers to the combination of all header values of the same name.
> 
> That would then mean that parsers, when seeing
> 
>>> Link: </a>; rel="describedBy"
>>> Link: </b>; rel="describedBy"
> 
> would, per 5.3., have to produce only
> 
>>> Link: </a>; rel="describedBy"
> 
> (ignoring the Link to /b)
> 
> Correct?
> 
> 
> P.S. I find that a bit counter intuitive. Given that further links might occur elsewhere in the entity.
> 
> Jan
> 
> 
> 
> 
> 
> 
> 
>> 
>> Semantically, in ANY HTTP header defined using the "," list production, the following are equivalent:
>> 
>> Foo: 1
>> Foo: 2
>> 
>> and
>> 
>> Foo: 1, 2
>> 
>> Regards,
>> 
>> 
>> On 21/10/2012, at 9:33 AM, Jan Algermissen <jan.algermissen@nordsc.com> wrote:
>> 
>>> Hi,
>>> 
>>> I am seeking a clarification ragarding link rel uniqueness in http://tools.ietf.org/html/rfc5988
>>> 
>>> AFAIU the required uniqueness of rel is 'per header' and thus, the following HTTP response headers in a single response would be valid according to RFC 5988:
>>> 
>>> 
>>> Link: </a>; rel="describedBy"
>>> Link: </b>; rel="describedBy"
>>> 
>>> Correct?
>>> 
>>> Jan
>>> _______________________________________________
>>> apps-discuss mailing list
>>> apps-discuss@ietf.org
>>> https://www.ietf.org/mailman/listinfo/apps-discuss
>> 
>> --
>> Mark Nottingham   http://www.mnot.net/
>> 
>> 
>> 
> 

--
Mark Nottingham   http://www.mnot.net/