(prefix ((x: <http://example/>))
  (test
    (join
      (table
        (row [?x 1] [?y x:g])
        (row [?x 2] ))
      (table 
        (row [?y x:g])
        (row [?x 2] )))
    (table
      (row [?y x:g] [?x 1])
      (row [?y x:g] [?x 2])
      (row [?x 2])
      )))