; define relations
(define object isa has)
; Elephants are animals.
(describe (assert object elephant isa animal))
; Circus elephants are elephants.
(describe (assert object circus-elephant isa elephant))
; Dumbo is a circus elephant.
(describe (assert object dumbo isa circus-elephant))
; Clyde is an elephant.
(describe (assert object clyde isa elephant))
; Trunks are appendages.
(describe (assert object trunk isa appendage))
; Alex is an AI course instructor.
(describe (assert object alex isa AICI))
; Tweety is a bird.
(describe (assert object tweety isa bird))
; Find out if Dumbo is an animal.
(describe (find object dumbo isa animal))
; Define the relation "isa" to be equivalent to an "isa"
; arc followed by 0 or more paths up an "object-" 
; arc to an asserted node and down to another "isa" arc:
(define-path isa (compose isa (kstar (compose object- ! isa))))
; Find out if Dumbo is an animal.
(describe (find object dumbo isa animal))
; Deduce whether Dumbo is an animal.
(describe (deduce object dumbo isa animal))