1

I am running bigdata 2.1.5 on a tomcat on a OSX system. This is giving a /bigdata/ URI which shows up a running html console of Blazegraph. This bigdata instance "DBPedia" is using a journal with DBPedia triples inside. DBPedia is showing up to the console, triples are queryable.

When I use from - say - https://query.wikidata.org/ - that bigdata instance by URI server/bigdata/namespace/DBPedia/sparql - that URI is not used, resp. the calling SPARQL engine throws an Exception that the service is not found.

Blazegraph has a page - https://wiki.blazegraph.com/wiki/index.php/FederatedQuery - where in a way it is described what to do in order to get federated querying running (although I want just to call my bigdata instance from outsite - this is also a federation) ... you should change (uncomment) a parametrization chunk inside bigdata's web.xml like

<context-param> <description>List of allowed services.</description>    <param-name>serviceWhitelist</param-name>   <param-value>http://www.bigdata.com/rdf/search#search,http://www.bigdata.com/rdf#describe</param-value> </context-param>

I changed that chunk but without success. Probably it is just to be able to call from that bigdata instance another service whose URI must be whitlisted. So I am stuck figuring out how to call my bigdata instance from - say wikidata - SPARQL engine...

Anyone an idea?

Stanislav Kralin
  • 11,070
  • 4
  • 35
  • 58
Fabio Ricci
  • 89
  • 1
  • 9
  • 1
    *"Probably it is just to be able to call from that bigdata instance another service whose URI must be whitlisted"* — yes, and probably you are not [whitelisted](https://www.mediawiki.org/wiki/Wikidata_Query_Service/User_Manual/SPARQL_Federation_endpoints) on Wikidata. – Stanislav Kralin Aug 20 '18 at 16:32

1 Answers1

0

The problem arose inside the calling SPARQL engine I used. Not in Blazegraph. So you have to check whether the SPARQL Engine you are currently using allows to open that URL inside a SERVICE expression (whitelisting)!

Fabio Ricci
  • 89
  • 1
  • 9
  • "Whitelisting" is necessary on some services (such as Wikidata). You might test on [a SPARQL endpoint which is configured to allow Federated SPARQL Queries against any remote endpoint](http://linkeddata.uriburner.com/sparql), such as that at [URIBurner](http://linkeddata.uriburner.com/) (does require that you authenticate with one of the supported services). [This article](https://medium.com/virtuoso-blog/5fb2b9f22ada) demonstrates Federated SPARQL against the public Wikidata and DBpedia SPARQL endpoints. – TallTed Aug 21 '18 at 21:05