Re: How do you explore a SPARQL Endpoint?

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
--------------------------------------------------------
*Mondeca*
35 boulevard de Strasbourg 75010 Paris
www.mondeca.com
Follow us on Twitter : @mondecanews <http://twitter.com/#%21/mondecanews>
----------------------------------------------------------