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Re: order within a @prefix

From: Ivan Herman <ivan@w3.org>
Date: Thu, 2 Dec 2010 13:53:58 +0100
Cc: Mark Birbeck <mark.birbeck@webbackplane.com>, Toby Inkster <tai@g5n.co.uk>, W3C RDFa WG <public-rdfa-wg@w3.org>
Message-Id: <2E3A0B7F-A3CA-46E2-B147-C3AEB5B24C20@w3.org>
To: Shane McCarron <shane@aptest.com>

On Dec 2, 2010, at 13:45 , Shane McCarron wrote:

> I think the attributes should be processed in DOM order, and that @profile is the exception, not the rule.  DOM order would also be consistent with xmlns:a=something xmlns:a=something else.  But this is definitely NOT editorial - which is why I think it needs to be a formal last call issue.

Right. I have created a 

http://www.w3.org/2010/02/rdfa/wiki/LC_CR_Comments

page for LC comments, and this has been added to it.


Ivan


> 
> On 12/2/2010 6:33 AM, Ivan Herman wrote:
>> Mark,
>> 
>> to be absolutely honest with you: I do not care. This is a typical edge case; no author in his/her able mind would do this anyway. But an implementation has to know, so we need a resolution. If we want to make use a virtual coin, that can also work...
>> 
>> Ivan
>> 
>> 
>> 
>> On Dec 2, 2010, at 13:14 , Mark Birbeck wrote:
>> 
>>> Hi Ivan,
>>> 
>>> I guess in one sense left-right v. right-left doesn't make much
>>> difference. However, our processing rules generally have a sort of
>>> 'later overrides earlier' aspect to them, based on the hierarchical
>>> nature of the documents that we're parsing. Having a rule where the
>>> deeper nodes override their parents' values makes processing very
>>> easy.
>>> 
>>> Now, of course you could say that 'latest wins' would still be the
>>> rule inside the @prefix attribute if we processed from right to left.
>>> But I do think that would be a little odd, given that conventionally
>>> people see the DOM hierarchy as going from left to right.
>>> 
>>> To illustrate, our processing model would say that the second
>>> occurrence of 'foaf' in this example applies due to the hierarchy (in
>>> a sense, it's 'later overrides earlier'):
>>> 
>>>  <div prefix="foaf: http://blah1">
>>>    <div prefix="foaf: http://blah2">
>>>      <!-- use blah2 --->
>>>    </div>
>>>  </div>
>>> 
>>> Writing an example where the same prefix is defined in @prefix might
>>> look like this:
>>> 
>>>  <div prefix="foaf: http://blah1
>>>                    foaf: http://blah2">
>>>      <!-- should really use blah2 --->
>>>    </div>
>>>  </div>
>>> 
>>> I think it would be counterintuitive if the left-most prefix was
>>> preferred over the right-most one, in this example.
>>> 
>>> This simplicity of overriding is lost in the processing of profiles
>>> (as a result of the resolution you refer to on ISSUE-23). The way that
>>> the processing is now described in section 9 implies that you need to
>>> track each profile loaded to see if there is a conflict later. Of
>>> course, the easiest way to implement this is to process from right to
>>> left, which removes the need to track each profile, but then I think
>>> most implementers will rightly ask...why is everything else going from
>>> left to right, except @profile?
>>> 
>>> We know that the only reason profile processing was made to work from
>>> right to left was due to the legacy use of @profile, in which only the
>>> first value had significance; some argued that this implied that the
>>> left-most profile should be the most important, and therefore should
>>> override others.
>>> 
>>> Personally, I didn't find this very convincing (and the resolution
>>> didn't have great support), but we have the resolution now.
>>> 
>>> However, given that we have the resolution to deal with a legacy
>>> issue, it should really be regarded as an anomaly, I it certainly
>>> shouldn't be used as a model for other processing rules.
>>> 
>>> Regards,
>>> 
>>> Mark
>>> 
>>> 
>>> On Thu, Dec 2, 2010 at 9:56 AM, Ivan Herman<ivan@w3.org>  wrote:
>>>> Shane,
>>>> 
>>>> there is no separate comment list; the reference in the document for comments is the WG mailing list...
>>>> 
>>>> But yes, this _is_ a last call comment, though I thought it is an editorial issue.
>>>> 
>>>> So, to make it clear, the question is what is the effect of @prefix="a: http://a.b a: http://c.d". In my original mail I said it should be left to right. But I since seemed to remember that we decided to have it right to left, ie, in my example, the result should be a->http://a.b. I tried to find a resolution in the mail archives, but I could not. However I did find this:
>>>> 
>>>> http://lists.w3.org/Archives/Public/public-rdfa-wg/2010May/0123.html
>>>> 
>>>> which led to a discussion thread on the relative priority within a @profile. This led to this resolution:
>>>> 
>>>> http://www.w3.org/2010/02/rdfa/meetings/2010-06-03#resolution_7
>>>> 
>>>> ie, left-most declaration wins. I have not found any resolutions related to @prefix. However, based on the the resolution we have already taken for @profile I would propose to define the same order for @prefix and that should be documented in RDFa 1.1 Core
>>>> 
>>>> Ivan
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On Dec 2, 2010, at 02:01 , Shane McCarron wrote:
>>>> 
>>>>> Since we are in last call, please submit this as a last call comment to the appropriate public list before the deadline.
>>>>> 
>>>>> On 12/1/2010 6:16 PM, Toby Inkster wrote:
>>>>>> On Wed, 1 Dec 2010 11:21:55 +0100
>>>>>> Ivan Herman<ivan@w3.org>   wrote:
>>>>>> 
>>>>>>> @prefix="a: http://a.b a: http://c.d"
>>>>>>> 
>>>>>>> will end in a->http://c.d
>>>>>>> 
>>>>>>> However, I tried to locate this in the document and I could not...
>>>>>> That's what I do, but I agree we need to make this explicit as it's a
>>>>>> case that implementors will definitely need to handle.
>>>>>> 
>>>>> --
>>>>> Shane P. McCarron                          Phone: +1 763 786-8160 x120
>>>>> Managing Director                            Fax: +1 763 786-8180
>>>>> ApTest Minnesota                            Inet: shane@aptest.com
>>>>> 
>>>>> 
>>>> 
>>>> ----
>>>> Ivan Herman, W3C Semantic Web Activity Lead
>>>> Home: http://www.w3.org/People/Ivan/
>>>> mobile: +31-641044153
>>>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>>>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>> 
>> ----
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>> 
>> 
>> 
>> 
>> 
> 
> -- 
> Shane P. McCarron                          Phone: +1 763 786-8160 x120
> Managing Director                            Fax: +1 763 786-8180
> ApTest Minnesota                            Inet: shane@aptest.com
> 
> 


----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf







Received on Thursday, 2 December 2010 12:51:39 UTC

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