An attribute-function is a unary function defined over model fragments or entities.
(<=> (Attribute-Function ?F) (And (Unary-Function ?F) (Domain ?F (Kappa (?X) (Or (Model-Fragment ?X) (Entity ?X))))))
(Domain ?F (Kappa (?X) (Or (Model-Fragment ?X) (Entity ?X)))) (Unary-Function ?F)
(<=> (Attribute-Function ?F) (And (Unary-Function ?F) (Domain ?F (Kappa (?X) (Or (Model-Fragment ?X) (Entity ?X)))))) (=> (Has-Attribute-Function $X $Y) (Attribute-Function $Y)) (=> (Attribute-Function-Total-On $X $Y) (Attribute-Function $X)) (<=> (Attribute-Function-Total-On ?Function ?Class) (And (Attribute-Function ?Function) (Class ?Class) (Total-On ?Function ?Class)))