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Re: Suggestion for Microdata to RDF conversion

From: Benjamin Nowack <bnowack@semsol.com>
Date: Thu, 21 Jan 2010 10:17:35 +0100
To: "Philip Jägenstedt" <philipj@opera.com>, public-html@w3.org
Message-ID: <PM-GA.20100121101735.3AB84.1.1D@semsol.com>

Hi Philip, thanks for the reply, but you missed my point ;)

I know the current conversion algorithm, but it leads to rather
ugly and unintuitive RDF. I was making a *suggestion* how 
Microdata could/should be converted to common RDF using very 
simple markup that would give RDFa a run for its money, within 
the boundaries of the Microdata syntax, and in line with RDF

I can still implement it via some easy post-processing and 
call it Microdata/RDF or some such, but I guess it makes 
sense if the *RDF* parts of Microdata are based on experience
and feedback from the RDF community and support relevant best 
practices. From an RDF POV, the prefixing/escaping of plain 
properties isn't required (if the motivation is to avoid
the creation of non-resolvable URIs). RDF encourages resolvable
term names, but tools can handle any sort of term just fine.

I *personally* wouldn't even specify anything RDF-ish in the 
Microdata spec directly at all. Just define the HTML-relevant 
syntax and DOM API and let the RDF community figure the
mapping out on their own. This worked for microformats, too.


Benjamin Nowack

On 21.01.2010 00:41:15, Philip Jägenstedt wrote:
>On Tue, 19 Jan 2010 18:17:19 +0100, Benjamin Nowack <bnowack@semsol.com>
>> Hi,
>> I'm working on a Microdata parser as part of an RDF toolkit. One thing
>> I've implemented but that isn't directly stated in the draft is the
>> generation of property URIs in the context of the itemtype. The spec
>> mentions that plain properties are to be used "within the context of
>> the types for which they are intended". And RDF vocabularies follow
>> the {namespace}/{type|prop} or {namespace}#{type|prop} pattern. So,
>> I made my parser extract the following RDF triples:
>>   _:bnode a <http://xmlns.com/foaf/0.1/Person> .
>>   _:bnode <http://xmlns.com/foaf/0.1/name> "Alec Tronnick" .
>>   _:bnode <http://xmlns.com/foaf/0.1/img> <mypic.jpg> .
>> from the Microdata snippet:
>>   <div itemscope="" itemtype="http://xmlns.com/foaf/0.1/Person">
>>     My name is <span itemprop="name">Alec Tronnick</span>
>>     <img itemprop="img" src="mypic.jpg" alt="" />
>>   </div>
>> as "name" and "img" are supposed to be applicable to the "Person"
>> type from the FOAF vocabulary. This sort of rule leads to very
>> compact markup in most single-vocab use cases (even more compact
>> and readable than RDFa's CURIEs) and simple authoring.
>> A sophisticated parser *could* GET and check the RDF vocabulary
>> for valid use of properties, but RDF does not have instance-level
>> validation, so the transparent expansion of plain property names
>> does not conflict with the RDF spec(trum). An author can of
>> course still use full URIs to mix in terms from other vocabs.
>If you follow the conversion algorithm at  
><http://dev.w3.org/html5/md/#rdf>, you'll find that your markup yields  
>something like these triples:
>@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
>_:n0 rdf:type <http://xmlns.com/foaf/0.1/Person> ;
>"Alec Tronnick" ;
><http://example.com/mypic.jpg> .
><http://www.w3.org/1999/xhtml/microdata#item> _:n0 .
>Note especially that mypic.jpg is resolved, here I assumed the markup was  
> from http://example.com/foo.html.
>To produce the triples you wanted, use this markup:
><div itemscope="" itemtype="http://xmlns.com/foaf/0.1/Person">
>   My name is <span itemprop="http://xmlns.com/foaf/0.1/name">Alec  
>   <img itemprop="http://xmlns.com/foaf/0.1/img" src="mypic.jpg" alt="" />
>As you can see, microdata has no prefix notation. To save yourself some  
>typing, use this:
><div itemscope itemtype="http://microformats.org/profile/hcard">
>   My name is <span itemprop="fn">Alec Tronnick</span>
>   <img itemprop="photo" src="mypic.jpg" alt="">
>If you actually wanted to use FOAF or care very much about the exact  
>triples, then the OWL needed to map the above to vCard RDF shouldn't be  
>very tricky, and I assume the relationship between FOAF and that is  
>already pretty clear.
>Philip Jägenstedt
>Core Developer
>Opera Software
Received on Thursday, 21 January 2010 09:18:06 UTC

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