@prefix rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rs:     <http://jena.hpl.hp.com/2003/03/result-set#> .

[] rdf:type rs:ResultSet ;
    rs:resultVariable "x" ;
    rs:resultVariable "y" ;
    rs:resultVariable "z" ;
    rs:size "0" ;
    .
