(deffacts date
  (fapt1 a b c alpha e)
  (fapt5 beta)
  (fapt2 x)
  (fapt3 "alpha beta gamma")
  (fapt4 alpha beta gamma)
)

(defrule test-str-index
  (fapt3 ?x)
  (fapt5 ?y)
  =>
  (assert (poz (str-index ?y ?x)))
)