(define-theory Artifacts (Actors))

(in-theory 'Artifacts)

(DEFINE-CLASS MACHINE-ACTIVITY (?SELF)
 "An activity carried out primarily or exclusively by machines." :IFF-DEF
 (AND (ACTIVITY ?SELF) (EXISTS (?A) (AND (EFFECTED-BY ?SELF ?A) (MACHINE ?A)))))
(DEFINE-CLASS MANUFACTURED-OBJECT (?SELF)
 "A physical object made by human beings." :DEF (ARTIFACT ?SELF))
(DEFINE-CLASS RESEARCH-DEVICE (?SELF)
 "A manufactured object used primarily in carrying out scientific research or 
experimentation."
 :DEF
 (AND (DEVICE ?SELF)
      (EXISTS (?A) (AND (USED-BY ?SELF ?A) (RESEARCH-ACTIVITY ?A)))))