Avoiding non-termination when learning logic programs: A case study with FOIL and FOCL

Abstract

Many systems that learn logic programs from examples adopt θ-subsumption as model of generalization and refer to Plotkin's framework in order to define their search space. However, they seldom take into account the fact that the lattice defined by Plotkin is a set of equivalence classes rather than simple clauses. This may lead to non-terminating learning processes, since the search gets stuck within an equivalence class, which contains an infinite number of clauses.