Computational Adequacy via "Mixed" Inductive Definitions

For programming languages whose denotational semantics uses xed points of domain constructors of mixed variance proofs of correspondence between operational and denotational semantics or be tween two di erent denotational semantics often depend upon the exis tence of relations speci ed as the xed point of non monotonic operators This paper describes a new approach to constructing such relations which avoids having to delve into the detailed construction of the recursively de ned domains themselves The method is introduced by example by considering the proof of computational adequacy of a denotational se mantics for expression evaluation in a simple untyped functional pro gramming language