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Re: Suggestion for Microdata to RDF conversion

From: Philip Jägenstedt <philipj@opera.com>
Date: Thu, 21 Jan 2010 21:00:54 +0100
To: bnowack@semsol.com, public-html@w3.org
Message-ID: <op.u6we7og4sr6mfa@worf>
I misunderstood what you were trying to do. Can you outline the steps  
needed to get the triples in your example? If you start out with  
http://xmlns.com/foaf/0.1/Person, name and img, would you HTTP GET  
http://xmlns.com/foaf/0.1/Person, hope to find an RDF Schema and find  
within it something relating to "name" and "img"? As far as I can see  
http://xmlns.com/foaf/0.1/Person redirects to an HTML page that uses RDFa  
to encode the RDF schema.


On Thu, 21 Jan 2010 10:17:35 +0100, Benjamin Nowack <bnowack@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
> concepts.
> 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.
> Benji
> --
> Benjamin Nowack
> http://bnode.org/
> http://semsol.com/
> On 21.01.2010 00:41:15, Philip Jägenstedt wrote:
>> On Tue, 19 Jan 2010 18:17:19 +0100, Benjamin Nowack <bnowack@semsol.com>
>> wrote:
>>> 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> ;
>> <http://www.w3.org/1999/xhtml/microdata#http%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2FPerson
>> %23%3Aname>
>> "Alec Tronnick" ;
>> <http://www.w3.org/1999/xhtml/microdata#http%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2FPerson
>> %23%3Aimg>
>> <http://example.com/mypic.jpg> .
>> <http://example.com/foo.html>
>> <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
>> Tronnick</span>
>>   <img itemprop="http://xmlns.com/foaf/0.1/img" src="mypic.jpg" alt=""  
>> />
>> </div>
>> 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="">
>> </div>
>> 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

Philip Jägenstedt
Core Developer
Opera Software
Received on Thursday, 21 January 2010 20:01:39 UTC

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