Re: [Virtuoso-users] Pass parameters to sparql

[Patrick van Kleef]

HI Mirko,

I have problems understanding parameters in sparql queries. I read
section 16.2.6 of the docs (http://docs.openlinksw.com/virtuoso/ 
rdfsparql.html#rdfsparqlinline
), but still don't succeed passing IRIs. I would appreciate an
example. E.g., how can I parametrize the object in the following  
query:

SELECT ?x FROM <http://www.mygraph.org> WHERE { ?x <http://purl.org/ 
dc/elements/1.1/creator
<http://myusers/xyz> }

My attempt (in Java) returns nothing, presumably because the parameter
is interpreted as a String value:

PreparedStatement stmt = con.prepareStatement("SELECT ?x FROM  
<http://www.mygraph.org
WHERE { ?x <http://purl.org/dc/elements/1.1/creator> ?? }");
stmt.setString(1, "http://myusers/xyz";);



I suggest you read the following part of the online documentation:

    http://docs.openlinksw.com/virtuoso/rdfapiandsql.html


As you indeed thought a parameter like "http://myusers/xyz"; is not  
the same as the <http://myusers/xyz>. In some constructions virtuoso  
is capable of determining the intended use of the parameter from the  
context like "graph ??", but in other cases a parameter will be  
interpreted as a String.

You can use the following construction (formatted for readability):

  PreparedStatement stmt = con.prepareStatement ("
    SELECT ?x FROM <http://www.mygraph.org>
    WHERE { ?x <http://purl.org/dc/elements/1.1/creator> `iri(??)` }
  ");

  stmt.setString(1, "http://myuser/xyz";);


Best regards,

Patrick