Knowledge Interchange Format (KIF) is a computer-oriented language for
the interchange of knowledge among disparate programs. It has
declarative semantics (i.e. the meaning of expressions in the
representation can be understood without appeal to an interpreter for
manipulating those expressions); it is logically comprehensive (i.e.
it provides for the expression of arbitrary sentences in the
first-order predicate calculus); it provides for the representation of
knowledge about the representation of knowledge; it provides for the
representation of nonmonotonic reasoning rules; and it provides for
the definition of objects, functions, and relations.