Query Stardog From Virtuoso

[Matías Parodi]

Hello guys,

I've been trying to query a Stardog DB from a Virtuoso endpoint using a query that looks like this:

SELECT *

FROM <http://localhost:5820/mydb/>

WHERE {

  GRAPH ?g {

    ?s ?p ?o

  }

}

Just to make it clear, mydb has a graph and inside this graph there are many triples, but unfortunately it returns nothing at all regardless of the URL I use in the FROM clause.

I saw how people use it for dbpedia and similar projects, the idea is that Virtuoso should create a cache with the triples that were missing, as shown in the <select> box in this screenshot: http://img23.imageshack.us/img23/1268/3y2s.png

Any idea?

Thanks,

Matt

[Mike Grove]

On Tue, Dec 3, 2013 at 10:06 PM, Matías Parodi <mparo...@gmail.com> wrote:

Hello guys,

I've been trying to query a Stardog DB from a Virtuoso endpoint using a query that looks like this:

SELECT *

FROM <http://localhost:5820/mydb/>

WHERE {

  GRAPH ?g {

    ?s ?p ?o

  }

}

Just to make it clear, mydb has a graph and inside this graph there are many triples, but unfortunately it returns nothing at all regardless of the URL I use in the FROM clause.

FROM/FROM NAMED don't work like that [1].  Some query engines will dereference the URL to get the RDF at the location, but I don't know if Virtuoso does that.  And even if it does, there's no RDF at that URL.

You probably want the SERVICE keyword.

Cheers,

Mike

[1] http://www.w3.org/TR/2013/REC-sparql11-query-20130321/#specifyingDataset

 

I saw how people use it for dbpedia and similar projects, the idea is that Virtuoso should create a cache with the triples that were missing, as shown in the <select> box in this screenshot: http://img23.imageshack.us/img23/1268/3y2s.png

Any idea?

Thanks,

Matt

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[Matías Parodi]

Here is an example of what I meant, with a screenshot of the result:

SELECT *
FROM <http://dbpedia.org/resource/Berlin>
WHERE {
 ?s ?p ?o
}
LIMIT 10

http://img36.imageshack.us/img36/7672/ye9h.png

http://img41.imageshack.us/img41/5251/y9g9.png

My intention is to use Virtuoso to query Stardog data like that, replacing http://dbpedia.org/resource/Berlin (which is the same as http://dbpedia.org/data/Berlin.n3) by <something>. What would this URL be?

[Matías Parodi]

Ah, you were right! It's possible to achieve what I'm looking for using the SERVICE keyword.

Unfortunately, it crashes as well...

SELECT *
WHERE {
  SERVICE <http://my_public_ip_here:5820/mydb#!/query> {

    ?s ?p ?o
  }
}
LIMIT 10

Virtuoso RDFZZ Error DB.DBA.SPARQL_REXEC('http://my_public_ip_here:5820/mydb#!/query', ...) returned unsupported Content-Type '(NULL)'

Any workaround?

[Mike Grove]

On Wed, Dec 4, 2013 at 6:34 PM, Matías Parodi <mparo...@gmail.com> wrote:

Ah, you were right! It's possible to achieve what I'm looking for using the SERVICE keyword.

Unfortunately, it crashes as well...

SELECT *
WHERE {
  SERVICE <http://my_public_ip_here:5820/mydb#!/query> {

    ?s ?p ?o
  }
}
LIMIT 10

Virtuoso RDFZZ Error DB.DBA.SPARQL_REXEC('http://mparodi.wildgeeks.com:5820/openfing#!/query', ...) returned unsupported Content-Type '(NULL)'

Any workaround?

Other than the URL should be http://my_public_ip_here:5820/mydb/query, no suggestions.  Not really familiar with how Virtuoso works, or doesn't, as the case may be.

Cheers,

Mike

[Matías Parodi]

The problem was in fact the URL, thank you so much!

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