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Re: The truth about SPARQL Endpoint availability

From: Michael Hausenblas <michael.hausenblas@deri.org>
Date: Sat, 5 Mar 2011 15:23:45 +0000
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: <0093576D-14B5-4B42-8792-2C27BA0B2229@deri.org>
To: Hugh Glaser <hg@ecs.soton.ac.uk>

> 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 ;)
Note that SCOVO modelling of stats in VoID has been deprecated and  
simplified [1].

> Fancy the challenge, it is the weekend?! :-)

Indeed!

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/
>
>
>
Received on Saturday, 5 March 2011 15:25:42 UTC

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