(select
 (join
  (join
   (leftjoin
    (bgp
      (triple ?:a <http://example/p> ?:c))
    (bgp
      (triple ?:a <http://example/r> ?:d)))
   (bgp
     (triple ?:a ?:p 1)))
  (union
   (bgp
     (triple ?:p |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:type ?:y))
   (bgp
     (triple ?:a ?:z ?:p))))
 (?:a ?:y ?:d ?:z))