Re: How do you explore a SPARQL Endpoint?

May be not just looking at the classes and properties but looking at their
frequencies using counts can give a better idea about what sort of data is
exposed. If there is a Void information it certainly helps. Tools such as
http://data.aalto.fi/visu also help. Similar approach described here [1] .

Best Regards,
Nandana

[1] - http://ceur-ws.org/Vol-782/PresuttiEtAl_COLD2011.pdf

On Thu, Jan 22, 2015 at 4:25 PM, Bernard Vatant <bernard.vatant@mondeca.com>
wrote:

> Interesting to note that the answers so far are converging towards looking
> first for types and predicates, but bottom-up from the data, and not
> queries looking for a declared model layer using RDFS or OWL, such as e.g.,
>
> SELECT DISTINCT ?class
> WHERE { {?class a owl:Class} UNION {?class a rdfs:Class}}
>
> SELECT DISTINCT ?property ?domain ?range
> WHERE { {?property rdfs:domain ?domain} UNION {?property rdfs:range
> ?range}}
>
> Which means globally you don't think the SPARQL endpoint will expose a
> formal model along with the data.
> That said, if the model is exposed with the data, the values of rdf:type
> will contain e.g., rdfs:Class and owl:Class ...
>
> Of course in the ideal situation where you have an ontology, the following
> would bring its elements.
>
> SELECT DISTINCT ?o ?x ?type
> WHERE {?x rdf:type ?type.
>                 ?x rdfs:isDefinedBy ?o.
>                 ?o a owl:Ontology }
>
> It's worth trying, because if the dataset you query is really big, it will
> be faster to look first for a declared model than asking all distinct
> rdf:type
>
>
> 2015-01-22 15:23 GMT+01:00 Alfredo Serafini <seralf@gmail.com>:
>
>> Hi
>>
>> the most basic query is the usual query for concepts, something like:
>>
>> SELECT DISTINCT ?concept
>> WHERE {
>> ?uri a ?concept.
>> }
>>
>> then, given a specific concept, you  can infer from the data what are the
>> predicates/properties for it:
>> SELECT DISTINCT ?prp
>> WHERE {
>> [] ?prp <a-concept>.
>> }
>>
>> and so on...
>>
>> Apart from other more complex query (here we are of course omitting a lot
>> of important things), these two "patterns" are usually the most useful as a
>> starting point, for me.
>>
>>
>>
>>
>> 2015-01-22 15:09 GMT+01:00 Juan Sequeda <juanfederico@gmail.com>:
>>
>>> Assume you are given a URL for a SPARQL endpoint. You have no idea what
>>> data is being exposed.
>>>
>>> What do you do to explore that endpoint? What queries do you write?
>>>
>>> Juan Sequeda
>>> +1-575-SEQ-UEDA
>>> www.juansequeda.com
>>>
>>
>>
>
>
> --
>
> *Bernard Vatant*
> Vocabularies & Data Engineering
> Tel :  + 33 (0)9 71 48 84 59
> Skype : bernard.vatant
> http://google.com/+BernardVatant
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