Characterizing Definability in Decidable Fixpoint Logics
Michael Benedikt, Pierre Bourhis, Michael Vanden Boom · DROPS (Schloss Dagstuhl – Leibniz Center for Informatics) · 2017
We look at characterizing which formulas are expressible in rich decidable logics such as guarded fixpoint logic, unary negation fixpoint logic, and guarded negation fixpoint logic. We consider semantic characterizations of definability, as well as effective characterizations. Our algorithms revolve around a finer analysis of the tree-model property and a refinement of the method of moving back-and-forth between relational logics and logics over trees.