@prefix rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rs:     <http://www.w3.org/2001/sw/DataAccess/tests/result-set#> .

[] rdf:type rs:ResultSet ;
    rs:resultVariable "a" ;
    rs:resultVariable "b" ;
    rs:size "0" ;
    .