@prefix : <#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix log: <http://www.w3.org/2000/10/swap/log.n3#> .

[ a rdf:Statement; 
  rdf:subject :x; 
  rdf:predicate :y; 
  rdf:object [ a rdf:Statement; 
  rdf:subject :x1; 
  rdf:predicate :y1; 
  rdf:object :z1 ] ] .