Hi all,
two years ago, we conducted an empirical experiment to find out how
promising the different approaches to discover SPARQL endpoints are. The
results were rather disappointing, see [1].
Executive summary: rather than trying to find VoID descriptions (which
rarely exist), querying catalogues like datahub seems more promising
(higher recall at least, precision is lower).
Hth.
Best,
Heiko
[1] http://www.heikopaulheim.com/docs/iswc2013_poster.pdf
Am 26.08.2015 um 11:50 schrieb Nandana Mihindukulasooriya:
Thanks all for the pointers.
Yes, it seems it is quite rare in practice. I tried several hosts that
provide Linked Data resources but couldn't find ones that provide a
VoID description in .well-known/void.
I guess there is a higher technical barrier in making that description
available in the given location compared to providing that information
in the response in most cases. So probably the pragmatic thing to do
would be to include this information either in the content or as a
Link relation header using the void properties when dereferenced.
So I can use the void:inDataset back-link mechanism [1] and point to a
VoID description that will have the necessary information about the
query endpoints.
-----
dbpedia:Sri_Lanka void:inDataset _:DBpedia .
_:DBpedia a void:Dataset;
void:sparqlEndpoint <http://dbpedia.org/sparql>;
void:uriLookupEndpoint <http://fragments.dbpedia.org/2014/en?subject=> .
------
or
----
Link: <http://dbpedia.org/void/Dataset>;
rel="http://rdfs.org/ns/void#inDataset";
----
Best Regards,
Nandana
[1] http://www.w3.org/TR/void/#discovery-links
On Wed, Aug 26, 2015 at 11:05 AM, Miel Vander Sande
<[email protected] <mailto:[email protected]>> wrote:
Hi Nandana,
I guess VoID would be the best fit
In case of LDF you could use
<...> void:uriLookupEndpoint
<http://fragments.dbpedia.org/2014/en?subject=>
But wether these exists in practice? Probably not. I'd leave it up
to the dereference publisher to provide this triple in te
response, rather than doing the .well_known thing.
Best,
Miel
On 26 Aug 2015, at 10:57, Víctor Rodríguez Doncel
<[email protected] <mailto:[email protected]>> wrote:
>
> Well, you might try to look in this folder location:
> .well-known/void
> And possibly find a "void:sparqlEndpoint".
>
> But this would be too good to be true.
>
> Regards,
> Víctor
>
> El 26/08/2015 10:45, Nandana Mihindukulasooriya escribió:
>> Hi,
>>
>> Is there a standard or widely used way of discovering a query
endpoint (SPARQL/LDF) associated with a given Linked Data resource?
>>
>> I know that a client can use the "follow your nose" and related
link traversal approaches such as [1], but if I wonder if it is
possible to have a hybrid approach in which the dereferenceable
Linked Data resources that optionally advertise query endpoint(s)
in a standard way so that the clients can perform queries on
related data.
>>
>> To clarify the use case a bit, when a client dereferences a
resource URI it gets a set of triples (an RDF graph) [2]. In some
cases, it might be possible that the returned graph could be a
subgraph of a named graph / default graph of an RDF dataset. The
client wants to discover if a query endpoint that exposes the
relevant dataset, if one is available.
>>
>> For example, something like the following using the "search"
link relation [3].
>>
>> ------
>> HEAD /resource/Sri_Lanka
>> Host: http://dbpedia.org
>> ------
>> 200 OK
>> Link: <http://dbpedia.org/sparql>; rel="search"; type="sparql",
<http://fragments.dbpedia.org/2014/en#dataset>; rel="search";
type="ldf"
>> ... other headers ...
>> ------
>>
>> Best Regards,
>> Nandana
>>
>> [1]
http://swsa.semanticweb.org/sites/g/files/g524521/f/201507/DissertationOlafHartig_0.pdf
>> [2]
http://www.w3.org/TR/2014/REC-rdf11-concepts-20140225/#section-rdf-graph
>> [3]
http://www.iana.org/assignments/link-relations/link-relations.xhtml
>
>
> --
> Víctor Rodríguez-Doncel
> D3205 - Ontology Engineering Group (OEG)
> Departamento de Inteligencia Artificial
> Facultad de Informática
> Universidad Politécnica de Madrid
>
> Campus de Montegancedo s/n
> Boadilla del Monte-28660 Madrid, Spain
> Tel. (+34) 91336 3672 <tel:%28%2B34%29%2091336%203672>
> Skype: vroddon3
>
>
> ---
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--
Prof. Dr. Heiko Paulheim
Data and Web Science Group
University of Mannheim
Phone: +49 621 181 2646
B6, 26, Room C1.08
D-68159 Mannheim
Mail: [email protected]
Web: www.heikopaulheim.com
