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Re: The truth about SPARQL Endpoint availability

From: Andrea Splendiani <andrea.splendiani@bbsrc.ac.uk>
Date: Sat, 5 Mar 2011 14:22:21 +0000
Cc: Pierre-Yves Vandenbussche <py.vandenbussche@gmail.com>, public-lod@w3.org, SW-forum <semantic-web@w3.org>, semanticweb@yahoogroups.com
Message-Id: <18C60386-35A0-4017-B9A2-B24217AE61CC@bbsrc.ac.uk>
To: Hugh Glaser <hg@ecs.soton.ac.uk>
Hi,

I think it depends on the store, I've tried some (from the endpoint list) and some returns a answer pretty quickly. Some doesn't and some doesn't support count.
However, one could have this information only for the stores that answers the count query, no need to try all time.

VoID:
is this a good query:
select * where {?s <http://rdfs.org/ns/void#numberOfTriples> ?o } 

it doesn't seem viable if so.

ciao,
Andrea


Il giorno 05/mar/2011, alle ore 13.49, Hugh Glaser ha scritto:

> NIce idea, but,... :-)
> 
> SELECT (count(*) as ?c) WHERE {?s ?p ?o}
> 
> is a pretty anti-social thing to do to a store.
> At best, a store of any size will spend a while thinking, and then quite rightly decide they have burnt enough resources, and return some sort of error.
> 
> For a properly maintained site, of course, the VoiD description will give lots of similar information.
> Best
> Hugh
> 
> On 5 Mar 2011, at 13:06, Andrea Splendiani wrote:
> 
>> Hi, very nice!
>> I have a small suggestion:
>> 
>> why don't you ask "count(*) where {?s ?p ?o}" to the endpoint ?
>> Or ask for the number of graphs ?
>> Both information, number of triples and number of graphs, if logged and compared over time, can give a practical view of the liveliness of the content of the endpoint.
>> 
>> best,
>> Andrea Splendiani
>> 
>> 
>> Il giorno 28/feb/2011, alle ore 18.55, Pierre-Yves Vandenbussche ha scritto:
>> 
>>> Hello all,
>>> 
>>> you have already encountered problems of SPARQL endpoint accessibility ?
>>> you feel frustrated they are never available when you need them?
>>> you develop an application using these services but wonder if it is reliable?
>>> 
>>> Here is a tool [1] that allows you to know public SPARQL endpoints availability and monitor them in the last hours/days. 
>>> Stay informed of a particular (or all) endpoint status changes through RSS feeds.
>>> All availability information generated by this tool is accessible through a SPARQL endpoint.
>>> 
>>> This tool fetches public SPARQL endpoints from CKAN  open data. From this list, it runs tests every hour for availability.
>>> 
>>> [1] http://labs.mondeca.com/sparqlEndpointsStatus/index.html
>>> [2] http://ckan.net/
>>> 
>>> Pierre-Yves Vandenbussche.
>> 
>> Andrea Splendiani
>> Senior Bioinformatics Scientist
>> Centre for Mathematical and Computational Biology
>> +44(0)1582 763133 ext 2004
>> andrea.splendiani@bbsrc.ac.uk
>> 
>> 
>> 
> 
> -- 
> Hugh Glaser,  
>              Intelligence, Agents, Multimedia
>              School of Electronics and Computer Science,
>              University of Southampton,
>              Southampton SO17 1BJ
> Work: +44 23 8059 3670, Fax: +44 23 8059 3045
> Mobile: +44 78 9422 3822, Home: +44 23 8061 5652
> http://www.ecs.soton.ac.uk/~hg/
> 
> 

Andrea Splendiani
Senior Bioinformatics Scientist
Centre for Mathematical and Computational Biology
+44(0)1582 763133 ext 2004
andrea.splendiani@bbsrc.ac.uk
Received on Saturday, 5 March 2011 14:28:50 UTC

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