Analyzing Context-Free Grammars Using an Incremental SAT Solver

Roland Axelsson, Keijo Heljanko, Martin Lange

Abstract: We consider bounded versions of undecidable problems about context-free languages which restrict the domain of words to some finite length: inclusion, intersection, universality, equivalence, and ambiguity. These are in (co)-NP and thus solvable by a reduction to the (un-)satisfiability problem for propositional logic. We present such encodings – fully utilizing the power of incrementat SAT solvers – prove correctness and validate this approach with benchmarks.