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Re: Cool URIs, the Semantic Web and Everything

From: Leo Sauermann <sauermann@dfki.uni-kl.de>
Date: Thu, 20 Dec 2007 02:43:09 +0000
Message-ID: <4769D6BD.1000904@dfki.uni-kl.de>
To: "Hausenblas, Michael" <michael.hausenblas@joanneum.at>
CC: semantic-web@w3.org, Leo Sauermann <leo.sauermann@dfki.de>

Hi Michael, RDFa people,

The question is if httpRange-14 [2] is valid in the case of XHTML+RDFa.

The answer is that httpRange-14 is to distinguish URIs for information 
resources ("web documents") from real-world objects (the person 
"Alice"). As such, it is a recommendation on URIs.

RDFa is an encoding of RDF, and typically an RDFa document has two 
relations to URIs:
a) the URI of the RDFa document (=the information resource where I can 
download the RDFa document)
b) the URIs used as subjects, predicates, objects inside RDF statements 
written inside RDFa documents

a) is usually a http-200 uri, and a) is an information resource (= a 
document).
In the rdf statemetns written inside  A, you would use both URIs for 
real-world objects and information resources.
example (I don't know  rdfa syntax by heart now, assume this is rdfa):

document at www.example.com/homepage/aboutAlice
<html>
<p rdf:about="http://www.example.com/identifiers/alice#this">
  rdf:type foaf:Person.
</p>
<p rdf:about="http://www.example.com/moreidentifiersusing303/bob">
 rdf:type foaf:Person
</p>
</html>

assuming this would be valid RDFa, the URI .../aboutAlice is a 
http-return-200 informaiton resource
..../alice#this is a real-world object as it is not a document (as I 
understand timbl on that)
....303/bob is not intuitively distinguishable - if you ignore the 
rdf:type relation you don't know what it is. So for this uri you do a 
HTTP get and the server would return a 303 redirect as described in 
"cool uris".
once oyu did the 303, you knowthat ....303/bob is a real world object.

so RDFa and 303'/httprange14 are recommendations caring about different 
angles, 303 is only concerned about URIs, RDFa about an RDF 
serialization. Technically they don't interfere.

If I would use RDFa much and would like cool uris, I would go for 
#-uris, they are simple to use and easy to embed in RDFa.
but as shown above, you can use any URI you want inside rdfa.

best
Leo


Hausenblas, Michael schrieb:
> ===
> Disclaimer: Michael, with his RDFa-Task-Force-member hat off ;)
> ===
>
> As I gathered "Cool URIs for the Semantic Web" is a Working Draft, now.
> Congrats to Leo and his team, great job! 
>
> The following might sound like a naive question - and I might 
> have missed something :) - but: Is TAG finding httpRange-14 [2] 
> equally valid in the case of XHTML+RDFa?
>
> I've put together some initial thoughts at the ESWiki [3]
> - any comments welcome!
>
> Cheers,
> 	Michael
>
> [1] http://lists.w3.org/Archives/Public/public-swd-wg/2007Dec/0103.html
> [2] http://www.w3.org/2001/tag/issues.html#httpRange-14
> [3] http://esw.w3.org/topic/RDFa_vs_RDFXML
>
> ----------------------------------------------------------
>  Michael Hausenblas, MSc.
>  Institute of Information Systems & Information Management
>  JOANNEUM RESEARCH Forschungsgesellschaft mbH
>  Steyrergasse 17, A-8010 Graz, AUSTRIA
>
>  <office>
>     phone: +43-316-876-1193 (fax:-1191)   
>    e-mail: michael.hausenblas@joanneum.at
>       web: http://www.joanneum.at/iis/ 
>
>  <private>
>    mobile: +43-660-7621761
>       web: http://www.sw-app.org/ 
> ----------------------------------------------------------
>
>   
Received on Wednesday, 26 December 2007 00:31:17 GMT

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