(deffacts dane
(inne dane)
(kolejne dane)
(cokolwiek)
(zeton1)
)

(defrule krok1
?i<-(zeton1)
=>
(retract ?i)
(assert (zeton2)))

(defrule krok2
?i<-(zeton2)
=>
(retract ?i)
(assert (zeton3)))

(defrule krok3
?i<-(zeton3)
=>
(retract ?i)
(assert (zeton1)))