Technical Report Number
Data, Theory of Computation, Computer Systems Organization
Typed homomorphic relations on heterogeneous algebras are generalized to allow relationships between elements in the carrier sets of different types. Such relations are needed for the model theory of incomplete, hierarchical specifications with subtypes. Typed logical relations are generalized similarly. These tools help give a simple model-theoretic account of subtyping among abstract data types as observed by terms of a simply-typed lambda-calculus with subtypes.