18 found
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  1.  22
    Instantial Neighbourhood Logic.Johan van Benthem, Nick Bezhanishvili, Sebastian Enqvist & Junhua Yu - 2017 - Review of Symbolic Logic 10 (1):116-144.
    This paper explores a new language of neighbourhood structures where existential information can be given about what kind of worlds occur in a neighbourhood of a current world. The resulting system of ‘instantial neighbourhood logic’ INL has a nontrivial mix of features from relational semantics and from neighbourhood semantics. We explore some basic model-theoretic behavior, including a matching notion of bisimulation, and give a complete axiom system for which we prove completeness by a new normal form technique. In addition, we (...)
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  2.  22
    A New Game Equivalence, its Logic and Algebra.Johan van Benthem, Nick Bezhanishvili & Sebastian Enqvist - 2019 - Journal of Philosophical Logic 48 (4):649-684.
    We present a new notion of game equivalence that captures basic powers of interacting players. We provide a representation theorem, a complete logic, and a new game algebra for basic powers. In doing so, we establish connections with imperfect information games and epistemic logic. We also identify some new open problems concerning logic and games.
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  3.  16
    A New Game Equivalence, its Logic and Algebra.Sebastian Enqvist, Nick Bezhanishvili & Johan Benthem - 2019 - Journal of Philosophical Logic 48 (4):649-684.
    We present a new notion of game equivalence that captures basic powers of interacting players. We provide a representation theorem, a complete logic, and a new game algebra for basic powers. In doing so, we establish connections with imperfect information games and epistemic logic. We also identify some new open problems concerning logic and games.
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  4.  16
    A Propositional Dynamic Logic for Instantial Neighborhood Semantics.Johan van Benthem, Nick Bezhanishvili & Sebastian Enqvist - 2019 - Studia Logica 107 (4):719-751.
    We propose a new perspective on logics of computation by combining instantial neighborhood logic \ with bisimulation safe operations adapted from \. \ is a recent modal logic, based on an extended neighborhood semantics which permits quantification over individual neighborhoods plus their contents. This system has a natural interpretation as a logic of computation in open systems. Motivated by this interpretation, we show that a number of familiar program constructors can be adapted to instantial neighborhood semantics to preserve invariance for (...)
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  5. Interrogative Belief Revision in Modal Logic.Sebastian Enqvist - 2009 - Journal of Philosophical Logic 38 (5):527-548.
    The well known AGM framework for belief revision has recently been extended to include a model of the research agenda of the agent, i.e. a set of questions to which the agent wishes to find answers (Olsson & Westlund in Erkenntnis , 65 , 165–183, 2006 ). The resulting model has later come to be called interrogative belief revision . While belief revision has been studied extensively from the point of view of modal logic, so far interrogative belief revision has (...)
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  6.  5
    A Propositional Dynamic Logic for Instantial Neighborhood Semantics.Sebastian Enqvist, Nick Bezhanishvili & Johan Benthem - 2019 - Studia Logica 107 (4):719-751.
    We propose a new perspective on logics of computation by combining instantial neighborhood logic $$\mathsf {INL}$$ INL with bisimulation safe operations adapted from $$\mathsf {PDL}$$ PDL. $$\mathsf {INL}$$ INL is a recent modal logic, based on an extended neighborhood semantics which permits quantification over individual neighborhoods plus their contents. This system has a natural interpretation as a logic of computation in open systems. Motivated by this interpretation, we show that a number of familiar program constructors can be adapted to instantial (...)
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  7.  21
    A Structuralist Framework for the Logic of Theory Change.Sebastian Enqvist - 2011 - In Erik J. Olson Sebastian Enqvist (ed.), Belief Revision Meets Philosophy of Science. Springer. pp. 105--135.
    Belief revision theory and philosophy of science both aspire to shed light on the dynamics of knowledge – on how our view of the world changes in the light of new evidence. Yet these two areas of research have long seemed strangely detached from each other, as witnessed by the small number of cross-references and researchers working in both domains. One may speculate as to what has brought about this surprising, and perhaps unfortunate, state of affairs. One factor may be (...)
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  8.  14
    Completeness for Μ-Calculi: A Coalgebraic Approach.Sebastian Enqvist, Fatemeh Seifan & Yde Venema - 2019 - Annals of Pure and Applied Logic 170 (5):578-641.
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  9.  15
    Contraction in Interrogative Belief Revision.Sebastian Enqvist - 2010 - Erkenntnis 72 (3):315 - 335.
    In the paper "On the role of the research agenda in epistemic change", Olsson and Westlund have suggested that the notion of epistemic state employed in the standard framework of belief revision (Alchourrón et al. 1985; Gärdenfors 1988) should be extended to include a representation of the agent's research agenda (Olsson and Westlund 2006). The resulting framework will here be referred to as interrogative belief revision. In this paper, I attempt to deal with the problem of how research agendas should (...)
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  10.  3
    Expressiveness of the Modal Mu-Calculus on Monotone Neighborhood Structures.Sebastian Enqvist, Fatemeh Seifan & Yde Venema - unknown
    We characterize the expressive power of the modal mu-calculus on monotone neighborhood structures, in the style of the Janin-Walukiewicz theorem for the standard modal mu-calculus. For this purpose we consider a monadic second-order logic for monotone neighborhood structures. Our main result shows that the monotone modal mu-calculus corresponds exactly to the fragment of this second-order language that is invariant for neighborhood bisimulations.
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  11.  16
    A General Lindström Theorem for Some Normal Modal Logics.Sebastian Enqvist - 2013 - Logica Universalis 7 (2):233-264.
    There are several known Lindström-style characterization results for basic modal logic. This paper proves a generic Lindström theorem that covers any normal modal logic corresponding to a class of Kripke frames definable by a set of formulas called strict universal Horn formulas. The result is a generalization of a recent characterization of modal logic with the global modality. A negative result is also proved in an appendix showing that the result cannot be strengthened to cover every first-order elementary class of (...)
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  12.  52
    Interrogative Belief Revision Based on Epistemic Strategies.Sebastian Enqvist - 2012 - Studia Logica 100 (3):453-479.
    I develop a dynamic logic for reasoning about "interrogative belief revision", a new branch of belief revision theory that has been developed in a small number of papers, beginning with E. J. Olsson and D. Westlund's paper "On the role of the research agenda in epistemic change" [12]. In interrogative belief revision, epistemic states are taken to include a research agenda, consisting of questions the agent seeks to answer. I present a logic for revision of such epistemic states based on (...)
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  13.  4
    Interrogative Belief Revision.Sebastian Enqvist - 2011 - Dissertation, Lund University
    This thesis deals with the theory of interrogative belief revision, a recent development in the subfield of philosophical logic known as belief revision theory. While classical belief revision theory deals with the dynamics of an agent’s beliefs, interrogative belief revision aims to describe the dynamics of the agent’s questions about the world, or research agenda, as well. Great emphasis is put on the interaction between belief change and changes in the research agenda. I develop both the technical framework for this (...)
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  14.  16
    Segerberg on the Paradoxes of Introspective Belief Change.Sebastian Enqvist & Erik J. Olsson - unknown
  15.  1
    A New Coalgebraic Lindström Theorem.Sebastian Enqvist - 2016 - Journal of Logic and Computation 26 (5):1541-1566.
    In a recent article, Alexander Kurz and Yde Venema establish a Lindström theorem for coalgebraic modal logic that is shown to imply a modal Lindström theorem by Maarten de Rijke. A later modal Lindström theorem has been established by Johan van Benthem, and this result still lacks a coalgebraic formulation. The main obstacle has so far been the lack of a suitable notion of ‘submodels’ in coalgebraic semantics, and the problem is left open by Kurz and Venema. In this article, (...)
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  16.  3
    Modelling Epistemic Actions in Interrogative Belief Revision.Sebastian Enqvist - 2012 - Journal of Logic and Computation 22 (6):1335-1365.
    in UndeterminedInterrogative belief revision is a relatively recent framework for belief revision theory, in which the epistemic state of an agent includes a representation of that agent's research agenda, i.e. the set of questions the agent wants to have answers to. This added structure opens new possibilites for various types of epistemic change that cannot be distinguished in traditional belief revision. In this article I use the so-called 'action model' approach known from the literature on dynamic epistemic logic to provide (...)
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  17.  5
    Editor's Introduction.Erik J. Olsson & Sebastian Enqvist - unknown
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  18.  1
    A Coalgebraic View of Characteristic Formulas in Equational Modal Fixed Point Logic.Sebastian Enqvist & Joshua Sack - unknown
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