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

Lee Feigenbaum lee at thefigtrees.net
Mon Apr 27 19:27:50 CEST 2009


Kingsley Idehen wrote:
> 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> .

"Should have" in what sense? :-)

I tried my original query that told me about the 1,330 blank nodes on 
dbpedia at this new endpoint, and it timed out.

Lee


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