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

Richard Cyganiak a écrit :
> 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. 
Suppose so. Maybe I was naively dreaming of  some "local transitivity" 
(say, 2 or 3 steps ...)
> 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. 
Yep. With neither loop nor meta-level consistency control ...
> 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... ;-)
Well, I did not figure it was *that* bad ... Makes me wonder if using 
skos:broader to express dbpedia categories "hierachy" is a good idea at 
all ...

Bernard
>
> 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 superseded by the new 2008 SKOS specification and namespace.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?
>>


-- 

*Bernard Vatant
*Senior Consultant
Vocabulary & Data Engineering
Tel:       +33 (0) 971 488 459
Mail:     bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com>
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Received on Tuesday, 21 October 2008 16:29:43 UTC