(prefix ((:  <http://example/>))

##   (diff 
##     (bgp (?a :p ?v ))
##     (filter (> ?v 23)
##       (bgp (?a :q ?w)))
##     )
  
     (filter (! (exists
                  (filter (> ?v 23)
                    (bgp (triple ?a :q ?w)))))
       (bgp (triple ?a :p ?v)))

  )