(module ancestors-vector mzscheme
  
  ;(require (planet "inference.ss" ("williams" "inference.plt")))
  (require "../inference.ss")
  
  ;;; Example Inference Model
  
  (define-ruleset ancestors-vector-ruleset)
  
  (define-rule (initialize ancestors-vector-ruleset)
      (?start <- (start))
    ==>
      (retract ?start)
      (printf "Please enter the first name of a~n")
      (printf "person whose ancestors you would~n")
      (printf "like to find:~n")
      (assert `#(request ,(read))))
  
  (define-rule (print-ancestors ancestors-vector-ruleset)
      (?request <- #(request ?name))
      #(parents ?name ?mother ?father)
    ==>
      (retract ?request)
      (when ?mother
        (printf "~a is an ancestor via ~a~n" ?mother ?name)
        (assert `#(request ,?mother)))
      (when ?father
        (printf "~a is an ancestor via ~a~n" ?father ?name)
        (assert `#(request ,?father))))
  
  (define-rule (remove-request ancestors-vector-ruleset)
      (?request <- #(request ?))
    ==>
      (retract ?request))
  
  (define (find-ancestors)
    (with-new-inference-environment
     (activate ancestors-vector-ruleset)
     ;(current-inference-trace #t)
     (assert '#(parents penelope jessica jeremy))
     (assert '#(parents jessica mary-elizabeth homer))
     (assert '#(parents jeremy jenny steven))
     (assert '#(parents steven loree john))
     (assert '#(parents loree #f jason))
     (assert '#(parents homer stephanie #f))
     (start-inference)))
  
  (find-ancestors)

  )