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Re: [Dbpedia-discussion] Looking for churches in Paris - skos:broader transitivity and dbpedia categories

From: Richard Cyganiak <richard@cyganiak.de>
Date: Tue, 21 Oct 2008 18:13:34 +0200
Cc: dbpedia-discussion@lists.sourceforge.net, SKOS <public-esw-thes@w3.org>
Message-Id: <0C7FCDB9-26B3-4E0D-99FB-9C8DB68D7E37@cyganiak.de>
To: Bernard Vatant <bernard.vatant@mondeca.com>

Bernard,

I don't know about plans regarding the namespace. Just one thing:  
Wikipedia categories are not transitive, and applying transitivity  
inference would produce undesirable results. This is because the  
category system is simply not a well-designed hierarchy, but rather a  
tagging system where categories can be tagged as well. For example, if  
we applied transitive inference, then category:Berlin would become a  
subcategory of category:Mexico, category:Asia, and category:Jesus.  
Don't ask why... ;-)

Best,
Richard


On 21 Oct 2008, at 12:27, Bernard Vatant wrote:

> Hi all
>
> I wanted to get at the following data set through http://dbpedia.org/sparql
>
> "Churches in Paris, along with French name and description, and
> geo-tagging elements"
>
> The category "Churches in Paris" has typically two levels of
> subcategories, by "Religion", then by "Arrondissement"
>
> So the following query
>
> PREFIX p: <http://dbpedia.org/property/>
> PREFIX dbpedia: <http://dbpedia.org/resource/>
> PREFIX category: <http://dbpedia.org/resource/Category:>
> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
> PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
> PREFIX geo: <http://www.georss.org/georss/>
>
> SELECT DISTINCT ?m ?n ?p ?d
> WHERE {
>    ?m rdfs:label ?n.
>    ?m skos:subject ?c.
>    ?c skos:broader category:Churches_in_Paris.
>    ?m p:abstract ?d.
>    ?m geo:point ?p
>   FILTER ( lang(?n) = "fr" )
>   FILTER ( lang(?d) = "fr" )}
>
> ... yields only the two results which are in a direct subcategory.  
> Which
> means skos:broader transitivity is not supported. OK.
> This leads to several remarks and questions.
> SKOS version declared in the namespace is the 2004 version, which is  
> now
> superseded by the new 2008 SKOS specification and namespace.
> For those not aware of the long debate history in SKOS about broader
> transitivity, the sum up is as following
>
> skos(2004):broader is transitive
> skos(2008):broader is no more transitive. It links only to the direct
> parent.
> skos(2008):broaderTransitive is a superproperty of the above, and it  
> is
> transitive - like skos(2004):broader
>
> To sum it up, the current dbpedia interface declares skos:broader in  
> the
> 2004 namespace, but de facto applies the 2008 semantics (no  
> transitivity).
> This is indeed confusing, and given there has been already a lot of
> confusion in people minds about that affair, it's too bad.
> Has dbpedia in project to switch from SKOS 2004 to SKOS 2008 namespace
> and semantics, and if yes when? And in such a case case, will it  
> support
> skos2008:broaderTransitive queries? As a side note, skos:subject is
> deprecated in SKOS 2008.
>
> Back to my churches in Paris, is there currently a workaround to get  
> the
> results for all subcategories in a single query?
>
> Thanks for your attention.
>
> -- 
>
> *Bernard Vatant
> *Senior Consultant
> Vocabulary & Data Engineering
> Tel:       +33 (0) 971 488 459
> Mail:     bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com 
> >
> ----------------------------------------------------
> *Mondeca**
> *3, citÚ Nollez 75018 Paris France
> Web:    www.mondeca.com <http://www.mondeca.com>
> Blog:    Lešons de Choses <http://mondeca.wordpress.com/>
> ----------------------------------------------------**
>
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Received on Tuesday, 21 October 2008 16:14:11 GMT

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