(select
 (filter
  (join
   (bgp
     (triple #S(SPOCQ:BLANK-NODE :ID COMMON-LISP:NIL :LABEL "a") ?:p ?:v))
   (bgp
     (triple ?::?74 ?:q #S(SPOCQ:BLANK-NODE :ID COMMON-LISP:NIL :LABEL "a"))))
  #S(SPOCQ:BOOLEAN
     :ID COMMON-LISP:NIL
     :LEXICAL-FORM "true"
     :VALUE COMMON-LISP:T))
 (?:p ?:v ?:q))