(select
 (leftjoin
  (bgp
    (triple ?:book <http://purl.org/dc/elements/1.1/title> ?:title))
  (bgp
    (triple ?:book <http://example.org/ns#price> ?:price))
  :TEST (&& (:< ?:price 15) (= ?:title "TITLE 2")))
 (?:title ?:price))