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Re: How do you explore a SPARQL Endpoint?

From: Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk>
Date: Fri, 23 Jan 2015 16:30:16 +0000
Message-ID: <CAPRnXtmkJuS+pi2i7LRL5eju0whV6U5uzdZZOikRu4VQH2X47A@mail.gmail.com>
To: Semantic Web <semantic-web@w3.org>, public-lod public <public-lod@w3.org>
The optimistic approach:

SELECT * WHERE {
  ?ontology a owl:Ontology .
  OPTIONAL { ?ontology owl:versionIRI ?version }
}

Then retrieve those separately over HTTP.

(Trying to extract the ontology over SPARQL would be much more work -
there might or might not live in separate graphs and might and might
not have proper isDefinedBy links)


On 23 January 2015 at 09:37, Pavel Klinov <pavel.klinov@uni-ulm.de> wrote:
> Alright, so this isn't an answer and I might be saying something
> totally silly (since I'm not a Linked Data person, really).
>
> If I re-phrase this question as the following: "how do I extract a
> schema from a SPARQL endpoint?", then it seems to pop up quite often
> (see, e.g., [1]). I understand that the original question is a bit
> more general but it's fair to say that knowing the schema is a huge
> help for writing meaningful queries.
>
> As an outsider, I'm quite surprised that there's still no commonly
> accepted (i'm avoiding "standard" here) way of doing this. People
> either hope that something like VoID or LOV vocabularies are being
> used, or use 3-party tools, or write all sorts of ad hoc SPARQL
> queries themselves, looking for types, object properties,
> domains/ranges etc-etc. There are also papers written on this subject.
>
> At the same time, the database engines which host datasets often (not
> always) manage the schema separately from the data. There're good
> reasons for that. One reason, for example, is to be able to support
> basic reasoning over the data, or integrity validation. Just because
> in RDF the schema language and the data language are the same, so
> schema and data triples can be interleaved, it need not (and often
> not) be managed that way.
>
> Yet, there's no standard way of requesting the schema from the
> endpoint, and I don't quite understand why. There's the SPARQL 1.1
> Service Description, which could, in theory, cover it, but it doesn't.
> Servicing such schema extraction requests doesn't have to be mandatory
> so the endpoints which don't have their schemas right there don't have
> to sift through the data. Also, schemas are typically quite small.
>
> I guess there's some problem with this which I'm missing...
>
> Thanks,
> Pavel
>
> [1] http://answers.semanticweb.com/questions/25696/extract-ontology-schema-for-a-given-sparql-endpoint-data-set
>
> On Thu, Jan 22, 2015 at 3:09 PM, Juan Sequeda <juanfederico@gmail.com> wrote:
>> 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
>



-- 
Stian Soiland-Reyes, eScience Lab
School of Computer Science
The University of Manchester
http://soiland-reyes.com/stian/work/    http://orcid.org/0000-0001-9842-9718
Received on Friday, 23 January 2015 16:31:13 UTC

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