Rum an intensional theory of function and control abstractions -- Typechecking dependent types and subtypes -- Reducing recursion to iteration by means of pairs and N-tuples -- Unification revisited -- Rule rewriting methods for efficient implementations of horn logic -- PAP: a logic programming system based on a constructive logic -- A completeness result for E-unification algorithms based on conditional narrowing -- Representing domain structure of many-sorted Prolog knowledge bases -- Horn: An inference engine prototype to implement intelligent systems -- Hints for the design of a set calculus oriented to Automated Deduction.