(aql-query
   ( select "s1" ( property any "root" subject ) )
   ( select "p1" ( property any "root" predicate ) )
   ( select "o1" ( property any "root" object ) )

   ( select "s2" ( property any "outerj" subject ) )
   ( select "p2" ( property any "outerj" predicate ) )
   ( select "o2" ( property any "outerj" object ) )
	
   (join left ("outerj") (comp-eq (property reference "root" object) (property reference "outerj" subject)))
)
