Hi Sebastian,
I completely agree with you. :-) And probably you agree with me in
saying that DBpedia _remote_ SPARQL endpoint will never give a response
to that query.
As you correctly said, the execution time set on remote DBpedia is too
short to complete such "complex" query.
I tried the same query on the Virtuoso Cluster Edition (8 server
processes) at http://lod.openlinksw.com/sparql/ (while
http://dbpedia.org/sparql has 4 server processes). But unfortunately the
result was the same: "Transaction timed out".
Me too, I run similar queries on our local server in our lab, configured
ad-hoc to extend execution time and allocated resources.
cheers,
roberto
Il 23/05/2011 18:38, Sebastian Hellmann ha scritto:
> Hi Roberto,
> sorry that I need to disagree, but DBpedia is based on Virtuoso, which
> has a quad model, i.e. a SQL table with 4 columns.
> The sparql query asks for all distinct values in the 3rd column and
> this is definitely doable seen from the SQL perspective.
> I normally run those queries on a daily basis and I even did the
> following query via sparql and it needed around 100 seconds:
> Select ?p count(?p) as ?count {?s ?p ?o } group by ?p order by DESC
> (?count)
> Results are here on 3.5.1:
> http://db0.aksw.org/downloads/propertyCount.csv.tar.gz
> I did these measurements on a local mirror on one of our servers.
>
> The problem is something else:
> - the main store is limited to a result set size of 1000 and has a
> limited execution time
> - getting a speedy answer depends on the traffic other users produce
> - currently there seems to be a bug causing an early transaction time out
>
> The only way to really do statistical measurements is to set up a
> local mirror and let queries run against this.
> Regards,
> Sebastian
>
> On 23.05.2011 18:16, Roberto Mirizzi wrote:
>> Il 23/05/2011 17:44, Sarasi Lalithsena ha scritto:
>>> Hi,
>>>
>>> I want to extract all properties from the DBpedia data set and I tried
>>> the following query but it did not work. I even tried to limit the
>>> results but still it did not work as well.
>>>
>>> select distinct ?property where {
>>> ?s ?property ?o .
>>> }
>>>
>>> I have the properties defined in the DBpedia Ontology but I am
>>> wondering whether their can be some other properties not defined in
>>> the ontology. If somebody can help me it would be a great help.
>> Hi Sarasi,
>> probably you will never get the expected results from that query. The
>> main problem is that you are asking DBpedia SPARQL endpoint to perform a
>> graph matching on all the 672 million triples in DBpedia, and then to
>> select distinct property.
>> This is too onerous, and the transaction will always time out.
>>
>>> Thank You
>>> Best Regards
>>> Sarasi Lalithsena
>> best regards,
>> roberto
>>
>
>
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