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Re: Using @resource instead of @about in RDFa Lite

From: Gregg Kellogg <gregg@kellogg-assoc.com>
Date: Thu, 17 Nov 2011 08:53:42 -0500
To: Ivan Herman <ivan@w3.org>
CC: Jeni Tennison <jeni@jenitennison.com>, Niklas Lindström <lindstream@gmail.com>, public-rdfa-wg <public-rdfa-wg@w3.org>, HTML Data Task Force WG <public-html-data-tf@w3.org>, Dan Brickley <danbri@danbri.org>, Ben Adida <ben@adida.net>
Message-ID: <D0B76A09-E07D-409E-A3B7-059AA0C8D9E6@kellogg-assoc.com>
On Nov 17, 2011, at 12:32 AM, "Ivan Herman" <ivan@w3.org> wrote:

> I essentially agree. In fact, I realized a while ago, when I played with the new @property setting in RDFa 1.1, that @resource might really be missing[1]. I must admit I did not think of dropping @about although, thinking about it further, having them both might be a bit complicated for the constituency of RDFa Lite.

Another reason to at least include @resourse is that, in HTML5, the content model for @href/@src and other native resource types, is a URL, not an IRI; in the DOM API, IRIs are actually transformed into URLs. If you want to have IRI resources, you'd need @resource.

In any case, I think that @resource creates less confusion than @about.

Gregg

> I have cc-d Ben explicitly, to see if there were some technical issues discussed on this that we may not know about.
> 
> Ivan
> 
> [1] http://lists.w3.org/Archives/Public/public-rdfa-wg/2011Nov/0024.html

> 
> On Nov 16, 2011, at 23:49 , Jeni Tennison wrote:
> 
>> 
>> On 16 Nov 2011, at 21:19, Niklas Lindström wrote:
>>> Have we considered whether @resource would be preferable over @about
>>> in RDFa Lite?
>> 
>> It's funny because I was just running into some issues that made me wish for @resource rather than @about.
>> 
>> @danbri set me the challenge of creating a stylesheet to map microdata into RDFa 1.1 Lite in part to easily generate some RDFa 1.1 Lite examples using schema.org markup.
>> 
>> The first document that I tried was http://www.imdb.com/title/tt0813715/. This contains the markup (much simplified here):
>> 
>> <div itemscope itemtype="http://schema.org/TVSeries">
>>   <div itemprop="aggregateRating" 
>>        itemscope itemtype="http://schema.org/AggregateRating">
>>     Ratings: 
>>     <strong><span itemprop="ratingValue">7.2</span></strong>
>>     <span class="mellow">/<span itemprop="bestRating">10</span></span> from 
>>     <a href="ratings" 
>>        title="23,201 IMDb users have given an average vote of 7.2/10">
>>       <span itemprop="ratingCount">23,201</span> users</a>
>>   </div>
>> </div>
>> 
>> which if you were to convert to RDF using the microdata/RDF mapping that Gregg's been working on, would generate something like:
>> 
>> <> md:item [ 
>>   a schema:TVSeries;
>>   schema:aggregateRating [ 
>>     a schema:AggregateRating;
>>     schema:bestRating "10";
>>     schema:ratingCount "23,201";
>>     schema:ratingValue "7.2"
>>   ]
>> ] .
>> 
>> A simplistic mapping into RDFa 1.1 gives:
>> 
>> <div vocab="http://schema.org/" typeof="TVSeries">
>>   <div property="aggregateRating" 
>>        vocab="http://schema.org/" typeof="AggregateRating">
>>     Ratings: 
>>     <strong><span property="ratingValue">7.2</span></strong>
>>     <span class="mellow">/<span property="bestRating">10</span></span> from 
>>     <a href="ratings" 
>>        title="23,201 IMDb users have given an average vote of 7.2/10">
>>       <span property="ratingCount">23,201</span> users</a>
>>   </div>
>> </div>
>> 
>> If you run that through a RDFa parser, you get:
>> 
>> [ 
>>   a schema:TVSeries;
>>   schema:aggregateRating [ 
>>     a schema:AggregateRating;
>>     schema:bestRating "10";
>>     schema:ratingValue "7.2"
>>   ]
>> ] .
>> 
>> <ratings> schema:ratingCount "23,201" .
>> 
>> What's happened? The ratingCount property is nested within a link, and the @href of the link is creating a new scope for the statements within that link, so instead of belonging to the AggregateRating, the ratingCount is a property of <ratings> (the URI of the link).
>> 
>> I can get around that in this case by adding a property="" to the link. However, if it had a @rel on it already, like this:
>> 
>> <div vocab="http://schema.org/" typeof="TVSeries">
>>   <div property="aggregateRating" 
>>        vocab="http://schema.org/" typeof="AggregateRating">
>>     Ratings: 
>>     <strong><span property="ratingValue">7.2</span></strong>
>>     <span class="mellow">/<span property="bestRating">10</span></span> from 
>>     <a href="ratings" rel="prefetch"
>>        title="23,201 IMDb users have given an average vote of 7.2/10">
>>       <span property="ratingCount">23,201</span> users</a>
>>   </div>
>> </div>
>> 
>> then that wouldn't work. In that case, I need to make sure that the subject of the ratingCount property is the aggregate rating, rather than <ratings>.
>> 
>> I could do that in two ways. One would be to add an @about attribute on both elements pointing to the same blank node, but in that case I'd need to create another nested <div> because if I put an @about attribute on the element with property="aggregateRating" then the subject of the triple generated by that property would be the @about. But then the property="aggregateRating" doesn't chain, so I'd have to use @rel:
>> 
>> <div vocab="http://schema.org/" typeof="TVSeries">
>>   <div rel="aggregateRating">
>>     <div about="_:rating" vocab="http://schema.org/" typeof="AggregateRating">
>>       Ratings: 
>>       <strong><span property="ratingValue">7.2</span></strong>
>>       <span class="mellow">/<span property="bestRating">10</span></span> from 
>>       <a href="ratings" rel="prefetch"
>>          title="23,201 IMDb users have given an average vote of 7.2/10">
>>         <span about="_:rating" property="ratingCount">23,201</span> users</a>
>>     </div>
>>   </div>
>> </div>
>> 
>> Or as Nicklas suggested I could use the @resource attribute. That works out a lot neater:
>> 
>> <div vocab="http://schema.org/" typeof="TVSeries">
>>   <div property="aggregateRating" resource="_:rating"
>>        vocab="http://schema.org/" typeof="AggregateRating">
>>     Ratings: 
>>     <strong><span property="ratingValue">7.2</span></strong>
>>     <span class="mellow">/<span property="bestRating">10</span></span> from 
>>     <a href="ratings" rel="prefetch" resource="_:rating"
>>        title="23,201 IMDb users have given an average vote of 7.2/10">
>>       <span property="ratingCount">23,201</span> users</a>
>>   </div>
>> </div>
>> 
>> Note that in neither case does the xhv:prefetch relationship make any sense whatsoever. Hopefully processors will ignore the bogus xhv:* properties.
>> 
>> @resource also gives a lot better mapping for @itemid. Say the microdata had an @itemid on the inner <div> like this:
>> 
>> <div itemscope itemtype="http://schema.org/TVSeries">
>>   <div itemprop="aggregateRating" 
>>        itemscope itemtype="http://schema.org/AggregateRating"
>>        itemid="ratings">
>>     Ratings: 
>>     <strong><span itemprop="ratingValue">7.2</span></strong>
>>     <span class="mellow">/<span itemprop="bestRating">10</span></span> from 
>>     <a href="ratings" 
>>        title="23,201 IMDb users have given an average vote of 7.2/10">
>>       <span itemprop="ratingCount">23,201</span> users</a>
>>   </div>
>> </div>
>> 
>> If @resource were allowed in RDFa 1.1 Lite then I could just map the @itemid to @resource really easily:
>> 
>> <div vocab="http://schema.org/" typeof="TVSeries">
>>   <div property="aggregateRating"
>>        vocab="http://schema.org/" typeof="AggregateRating"
>>        resource="ratings">
>>     Ratings: 
>>     <strong><span property="ratingValue">7.2</span></strong>
>>     <span class="mellow">/<span property="bestRating">10</span></span> from 
>>     <a href="ratings"
>>        title="23,201 IMDb users have given an average vote of 7.2/10">
>>       <span property="ratingCount">23,201</span> users</a>
>>   </div>
>> </div>
>> 
>> So I strongly support Niklas' suggestion of using @resource rather than @about in RDFa 1.1 Lite.
>> 
>> Cheers,
>> 
>> Jeni
>> -- 
>> Jeni Tennison
>> http://www.jenitennison.com

>> 
>> 
> 
> 
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/

> mobile: +31-641044153
> FOAF: http://www.ivan-herman.net/foaf.rdf

> 
> 
> 
> 
> 
> 
Received on Thursday, 17 November 2011 13:54:19 GMT

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