[foaf-dev] [foaf-protocols] FOAF sites offline during cleanup

Kingsley Idehen kidehen at openlinksw.com
Mon Apr 27 19:12:13 CEST 2009


Lee Feigenbaum wrote:
> [trimmed to: and cc: list a bit]
>
> Kingsley Idehen wrote:
>> Dan Brickley wrote:
>>>
>>> What % of "linked data" is truly free of bnodes?
>>>   
>> Dan,
>>
>> I would safely say re. LOD Cloud somewhere north of 80% :-) And thats 
>> primary due to the content coming from PingTheSemanticWeb, otherwise 
>> I would say 90% and higher. The "Linked Data" meme has always 
>> encouraged URIs for everything.
>
> This discussion is interesting to me. Kingsley's comment made me say 
> "huh, does dbpedia really only use URIs?"
>
> so I ran:
>
> select count(distinct ?s) where { ?s ?p ?o . filter(isblank(?s)) }
>
> at http://dbpedia.org/sparql and received a result of 1330.
>
> (i trired to compare with URIs by querying with isuri or with no 
> filter, but those queries timed out)
>
> so there seem to be a few blank nodes scattered there, but not many. i 
> wanted to get an idea of what these blank nodes are used for, so i did:
>
> select distinct ?p where { ?s ?p ?o . filter(isblank(?s)) }
>
> http://www.w3.org/1999/02/22-rdf-syntax-ns#type
> http://www.w3.org/2002/07/owl#unionOf
> http://www.w3.org/1999/02/22-rdf-syntax-ns#first
> http://www.w3.org/1999/02/22-rdf-syntax-ns#rest
>
> ...which made it somewhat clear that blank nodes are used in dbpedia 
> for RDF lists and (?) anonymous classes.
>
> Anyway.
>
> Lee
>
Lee,

Nice analysis, but you should have used: 
http://lod.openlinksw.com/sparql (this is the LOD cloud datasets in a 
Virtuoso Cluster, and its much faster).

If you want to scope your query to DBpedia then just use the Graph IRI: 
<http://dbpedia.org> .


-- 


Regards,

Kingsley Idehen	      Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO 
OpenLink Software     Web: http://www.openlinksw.com






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