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

Lee Feigenbaum lee at thefigtrees.net
Mon Apr 27 18:05:27 CEST 2009


[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


More information about the foaf-dev mailing list