Proving Properties of Constraint Logic Programs by Eliminating Existential Variables

We propose a method for proving first order properties of constraint logic programs which manipulate finite lists of real numbers. Constraints are linear equations and inequations over reals. Our method consists in converting any given first order formula into a stratified constraint logic program and then applying a suitable unfold/fold transformation strategy that preserves the perfect model. Our strategy is based on the elimination of existential variables, that is, variables which occur in the body of a clause and not in its head. Since, in general, the first order properties of the class of programs we consider are undecidable, our strategy is necessarily incomplete. However, experiments show that it is powerful enough to prove several non-trivial program properties.