A Connection between Cantor-Bendixson Derivatives and the Well-Founded Semantics of Logic Programs.

We show that there is a close connection between the con- struction of the perfect kernel of a 0 1 class via the intera- tion of the Cantor-Bendixson derivative through the ordinals and the construction of the well-founded semantics for logic programs via Van Gelder's alternating fixpoint construction. This connection allows us to transfer known complexity re- sults for the perfect kernel of 0 1 classes to to give new com- plexity results for various questions about the well-founded semanticswfs(P ) of a logic programP .