(define (domain transport)
  (:requirements :durative-actions :typing :fluents :adl :constraints :preferences)
  (:types
	location person - object
	street - location
  )
  (:predicates 
	(in ?x - person ?y - location)
	(link ?x - location ?y - location)
	(not_used_feet)
  )
  (:functions 
	(minutes)
	(money ?p - person)
        (distance)
	
  )
;; a person moves between two locations if there exist a link between these locations.
 (:durative-action walk
    :parameters (?p - person ?l1 - location ?l2 - location)
    :duration (= ?duration (minutes))
    :condition (and 
		    (at start (in ?p ?l1))
		    (over all (link ?l1 ?l2))
                )

    :effect (and (at start (not(in ?p ?l1)))
                 (at end (in ?p ?l2))
	         (at end (increase (money ?p)
					(distance)))
		 (at end (not (not_used_feet)))
	    )
 )
)