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Re: Display values for RDFa object URLs

From: Ivan Herman <ivan@w3.org>
Date: Fri, 10 Aug 2007 10:27:28 +0200
Message-ID: <46BC2170.5090603@w3.org>
To: Mark Birbeck <mark.birbeck@formsPlayer.com>
CC: Manu Sporny <msporny@digitalbazaar.com>, RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>
I understand the intention, I see the solution, but I am not convinced:-(.

I think we should keep such 'implicit' rules of triple generation to the
minimum. We try to second guess the author's intentions here and I am
not sure that is justified. There are a number of Web pages, for
example, that use the (absolutely horrible!) 'click here' or 'see here',
or similar content to <a>. Yes, it is a very bad design, but it is
there. Ie, we will get a bunch of meaningless rdfs:label-s...

As you say, the construction:

<div about="#song" instanceof="hmedia:Audio">
 <a rel="hmedia:sample" href="http://www.bitmunk.com/sample/6011101">
       <span property="rdfs:label">A Sample</span>
 </a>
</div>

works, it makes it explicit what the user wants, and also gives him/her
to possibility to fine tune what should be a label and what shouldn't.

It also opens the flood gates to a bunch of other questions. Do you want
to introduce the same mechanism everywhere where one would use @href
(after all, we opened this particular flood gate by allowing @href
everywhere!)? What happens if I use @resource on <a> but no @href? What
happens if there is additional markup within <a>? All set of additional
issues that (1) has to be answered (2) has to be specified in the
syntax, thereby making it more complicated (3) has to be properly
explained in a primer document (4) has to be documented with test cases,
etc, etc. I just do not see that avoiding one additional <span>
justifies these costs...

I would propose to keep this out for the moment.

My two pence...

Ivan


Mark Birbeck wrote:
> Hi Manu,
> 
>> If we could get rid of that extra <span> around the "A Sample" text...
>> that would be great. That would help make the HTML far less verbose...
>> is the following what we're talking about doing?
>>
>> <div about="#song" instanceof="hmedia:Audio">
>>  <a rel="hmedia:sample" property="rdfs:label"
>>     href="http://www.bitmunk.com/sample/6011101">
>>        A Sample
>>  </a>
>> </div>
> 
> The answer to your question will hopefully be the result of my action
> item to "work rdfs:label back in". :) This is a reference to the fact
> that we used to have support for rdfs:label in early drafts of RDFa,
> but it was dropped. However, I think the reversion back to the old
> technique of chaining might actually solve this problem (and allow me
> to tick off an action item). So I'd appreciate comments from
> interested parties, on the following proposal.
> 
> First to indicate what I'm trying to achieve. My goal is that by
> simply writing this:
> 
>   <div about="#song" instanceof="hmedia:Audio">
>     <a rel="hmedia:sample" href="http://www.bitmunk.com/sample/6011101">
>       A Sample
>     </a>
>   </div>
> 
> the parser will create "A Sample" as an rdfs:label 'for free'.
> 
> However, every time I look at this, the problem has been what to
> attach this label to. The only option that had any legs was to simply
> generate it based on the parent subject:
> 
>   <#song>
>     [
>       rdf:type hmedia:Audio;
>       hmedia:sample <http://www.bitmunk.com/sample/6011101>;
>       rdfs:label "A Sample"
>     ] .
> 
> But I was never happy with this because it is labelling the 'song',
> rather than the link to the sample (which might be different).
> However, in the chaining rules, @href would actually become the
> subject for any nested RDFa statements, which means that this:
> 
>   <div about="#song" instanceof="hmedia:Audio">
>     <a rel="hmedia:sample" href="http://www.bitmunk.com/sample/6011101">
>       <span property="rdfs:label">A Sample</span>
>     </a>
>   </div>
> 
>  would give us something which I think is more useful (and logical):
> 
>   <#song>
>     [
>       rdf:type hmedia:Audio;
>       hmedia:sample <http://www.bitmunk.com/sample/6011101>
>     ] .
>   <http://www.bitmunk.com/sample/6011101> rdfs:label "A Sample" .
> 
> My proposal would be to *automatically* generate an RDFS label for the
> text content of any <a> element. The justification for this is that
> this is actually what the author is already doing, and so the
> semantics are actually correct. I.e., this is all that is needed:
> 
>   <div about="#song" instanceof="hmedia:Audio">
>     <a rel="hmedia:sample" href="http://www.bitmunk.com/sample/6011101">
>       A Sample
>     </a>
>   </div>
> 
> (One of the main motivations for this approach was actually the use
> that could be made of this by search engines.)
> 
> Regards,
> 
> Mark
> 

-- 

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


Received on Friday, 10 August 2007 08:27:53 GMT

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