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Re: How do you explore a SPARQL Endpoint?

From: Pavel Klinov <pavel.klinov@uni-ulm.de>
Date: Fri, 23 Jan 2015 10:37:49 +0100
Message-ID: <CAG5JQxXTfQRnoH5CkjcDG59C3EAmMGgHiYpwG+8mm4ct_rzkqA@mail.gmail.com>
To: Juan Sequeda <juanfederico@gmail.com>
Cc: Semantic Web <semantic-web@w3.org>, public-lod public <public-lod@w3.org>
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...


[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
Received on Friday, 23 January 2015 09:38:21 UTC

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