How to discover the capabilities of a SPARQL endpoint en route to enhancing SPARQL-FED usage from Virtuoso instances.

There are features supported in Virtuoso SPARQL that aren't supported by other SPARQL engines. There are also a lot of Virtuoso instances behind bubbles in the LOD cloud. Net effect, a Virtuoso instance operator is faced with varied behavior when attempting to use SPARQL-FED functionality.

Run this command to load metadata (or lack thereof) from an external SPARQL endpoint:

SPARQL LOAD SERVICE <{sparql-endpoint-iri> DATA
  1. Run:

    Query result:
    ANY
     Load service <http://lod.openlinksw.com/sparql> data -- done.
     Trying to query <http://lod.openlinksw.com/sparql> as SPARQL web service endpoint, POST mode...
    
  2. Check the retrieved data:

    SPARQL
    SELECT *
      FROM virtrdf:
     WHERE
         {
           <http://lod.openlinksw.com/sparql> ?p ?o
         }
     LIMIT 10
    
    Query result:
    p                                                                o
    ANY                                                              ANY
    http://www.openlinksw.com/schemas/virtrdf#isEndpointOfService      http://lod.openlinksw.com/sparql-sd
    http://www.openlinksw.com/schemas/virtrdf#dialect                000037ff