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Re: The truth about SPARQL Endpoint availability

From: Hugh Glaser <hg@ecs.soton.ac.uk>
Date: Sat, 5 Mar 2011 15:46:06 +0000
To: Michael Hausenblas <michael.hausenblas@deri.org>
CC: Andrea Splendiani <andrea.splendiani@bbsrc.ac.uk>, Pierre-Yves Vandenbussche <py.vandenbussche@gmail.com>, "<public-lod@w3.org>" <public-lod@w3.org>, SW-forum <semantic-web@w3.org>, "<semanticweb@yahoogroups.com>" <semanticweb@yahoogroups.com>
Message-ID: <EMEW3|30770e8a4bd4660251b753b7f1d90ae6n24FkX02hg|ecs.soton.ac.uk|075AAFE6-94E8-45CB-822C-466C360844D0@ecs.soton.ac.uk>

On 5 Mar 2011, at 15:23, Michael Hausenblas wrote:

> 
>> I'm no SPARQL or voiD guru, but I think you need a bit more wrapping in the scovo stuff, so more like:
> ROTFL, reading that Hugh claims to be *not* a VoID guru ;)
Tee hee.
Very kind, but
> Note that SCOVO modelling of stats in VoID has been deprecated and simplified [1].

sort of proves my assertion :-)
And perhaps this little interchange proves the assertion in [1]
"Statistics would be verbose, and querying them with SPARQL was difficult."

I was looking at our voiD docs.
Seems we have not updated them, and they still do scovo.
Better make sure the boys get to work :-)
> 
>> Fancy the challenge, it is the weekend?! :-)
> 
> Indeed!
Cheers
> 
> Cheers,
> 	Michael
> [1] http://www.w3.org/TR/void/#statistics
> --
> Dr. Michael Hausenblas, Research Fellow
> LiDRC - Linked Data Research Centre
> DERI - Digital Enterprise Research Institute
> NUIG - National University of Ireland, Galway
> Ireland, Europe
> Tel. +353 91 495730
> http://linkeddata.deri.ie/
> http://sw-app.org/about.html
> 
> On 5 Mar 2011, at 15:14, Hugh Glaser wrote:
> 
>> Hi,
>> On 5 Mar 2011, at 14:22, Andrea Splendiani wrote:
>> 
>>> 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.
>> I am happy for a store implementor or owner to disagree, but I find it very unlikely that the owner of a store with a decent chunk of data (> 1M triples, say) would be happy for someone to keep issuing such a query, even if they did decide to give enough resources to execute it.
>> I would quickly blacklist such a site.
>>> 
>>> VoID:
>>> is this a good query:
>>> select * where {?s <http://rdfs.org/ns/void#numberOfTriples> ?o }
>> 
>> I'm no SPARQL or voiD guru, but I think you need a bit more wrapping in the scovo stuff, so more like:
>> 
>> SELECT DISTINCT ?endpoint ?uri ?triples ?uris WHERE
>>          { ?ds a void:Dataset .
>>            ?ds void:sparqlEndpoint ?uri .
>>            ?ds rdfs:label ?endpoint .
>>            ?ds void:statItem [ scovo:dimension void:numberOfTriples ; rdf:value  ?triples ] .
>>         }
>> 
>> Try it at
>> http://kwijibo.talis.com/voiD/
>> or
>> http://void.rkbexplorer.com/
>> 
>> I guess Pierre-Yves might like to enhance his page by querying a voiD store to also give basic stats.
>> Or someone might like to do a store reporter that uses (a) voiD endpoint(s) plus Pierre-Yves's data (he has a SPARQL endpoint), to do so.
>> And maybe the CKAN endpoint would have extra useful data as well.
>> A real Semantic Web application that queried more than one SPARQL endpoint - now that would be a novelty!
>> Fancy the challenge, it is the weekend?! :-)
>> 
>> ciao
>> Hugh
>> 
>>> 
>>> 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
>>> 
>>> 
>>> 
>> 
>> -- 
>> 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/
>> 
>> 
>> 
> 

-- 
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/
Received on Saturday, 5 March 2011 15:49:18 UTC

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