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

Kingsley Idehen kidehen at openlinksw.com
Tue Apr 28 14:56:53 CEST 2009


Lee Feigenbaum wrote:
> 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
>
Lee,

To close the loop re. this thread, the issue you had with the LOD 
instance  comes down to the fact that we split the DBpedia ontology and 
instance data into separate Graphs. Thus it would have worked using:

DBpedia Ontology IRI: <http://dbpedia.org/resource/classes#>
DBpedia Instance Data: <http://dbpedia.org>

Since the ontology isn't really that large, we've also loaded it into 
Graph IRI: <http://dbpedia.org>.

You can now repeat your tests using 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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