Monotone Subintuitionistic Logic: Duality and Transfer Results.Jim de Groot &Dirk Pattinson -2022 -Notre Dame Journal of Formal Logic 63 (2):213-242.detailsWe consider subintuitionistic logics as an extension of positive propositional logic with a binary modality, interpreted over ordered and unordered monotone neighborhood frames, with a range of frame conditions. This change in perspective allows us to apply tools and techniques from the modal setting to subintuitionistic logics. We provide a Priestley-style duality, and transfer results from the (classical) logic of monotone neighborhood frames to obtain completeness, conservativity, and a finite model property for the basic logic, extended with a number of (...) axioms. (shrink)
Expressive Logics for Coalgebras via Terminal Sequence Induction.Dirk Pattinson -2004 -Notre Dame Journal of Formal Logic 45 (1):19-33.detailsThis paper presents a logical characterization of coalgebraic behavioral equivalence. The characterization is given in terms of coalgebraic modal logic, an abstract framework for reasoning about, and specifying properties of, coalgebras, for an endofunctor on the category of sets. Its main feature is the use of predicate liftings which give rise to the interpretation of modal operators on coalgebras. We show that coalgebraic modal logic is adequate for reasoning about coalgebras, that is, behaviorally equivalent states cannot be distinguished by formulas (...) of the logic. Subsequently, we isolate properties which also ensure expressiveness of the logic, that is, logical and behavioral equivalence coincide. (shrink)