%META:TOPICPARENT{name="VirtTipsAndTricksGuide"}%

---+How to discover the capabilities of a SPARQL endpoint to enhancing SPARQL-FED usage from Virtuoso instances using LOAD SERVICE ... DATA

---++What?
How to discover the capabilities of a SPARQL endpoint en route to enhancing SPARQL-FED usage from Virtuoso instances using LOAD SERVICE ... DATA.

---++Why?

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.

---++How?

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

<verbatim>
SPARQL LOAD SERVICE <sparql-endpoint-iri> DATA 
</verbatim>

---+++Example

   1 Load [[http://lod.openlinksw.com][LOD]] SPARQL Endpoint data:
<verbatim>
SPARQL LOAD SERVICE <http://lod.openlinksw.com/sparql> DATA 

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...
</verbatim>
   2 Check the loaded data:
<verbatim>
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
</verbatim>


---++Additional Usage Benefits


Suppose one queries a remote endpoint and get sort of <i>"Unsupported .. "</i> kind of errors -- the proper solution is to run <code>SPARQL LOAD SERVICE DATA</code>. If however the error persists, one should rephrase the query as the remote can't handle the query in its current form.


---++Related

   * [[VirtTipsAndTricksGuide][Virtuoso Tips and Tricks Collection]]
   * [[VirtTipsAndTricksDiscoverSPARQFedCapabilitiesSPARQL][Adding SPARQL Endpoint Capabilities Interrogation to Virtuoso SPARQL-FED functionality]]