- From: Kingsley Idehen <kidehen@openlinksw.com>
- Date: Mon, 27 Apr 2009 13:12:13 -0400
- To: Lee Feigenbaum <lee@thefigtrees.net>
- CC: Dan Brickley <danbri@danbri.org>, foaf-dev Friend of a <foaf-dev@lists.foaf-project.org>, Semantic Web <semantic-web@w3.org>
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
Received on Monday, 27 April 2009 17:12:54 UTC