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  1. Global and Iterated Contraction and Revision: An Exploration of Uniform and Semi-Uniform Approaches. [REVIEW]Sven Ove Hansson - 2012 - Journal of Philosophical Logic 41 (1):143-172.
    In order to clarify the problems of iterated (global) belief change it is useful to study simple cases, in particular consecutive contractions by sentences that are both logically and epistemically independent. Models in which the selection mechanism is kept constant are much more plausible in this case than what they are in general. One such model, namely uniform specified meet contraction, has the advantage of being closely connected with the AGM model. Its properties seem fairly adequate for the intended type (...)
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  • Repertoire Contraction.Sven Ove Hansson - 2013 - Journal of Logic, Language and Information 22 (1):1-21.
    The basic assumption of repertoire contraction is that only some of the logically closed subsets of the original belief set are viable as contraction outcomes. Contraction takes the form of choosing directly among these viable outcomes, rather than among cognitively more far-fetched objects such as possible worlds or maximal consistent subsets of the original belief set. In this first investigation of repertoire contraction, postulates for various variants of the operation are introduced. Necessary and sufficient conditions are given for when repertoire (...)
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  • Blockage Contraction.Sven Ove Hansson - 2013 - Journal of Philosophical Logic 42 (2):415-442.
    Blockage contraction is an operation of belief contraction that acts directly on the outcome set, i.e. the set of logically closed subsets of the original belief set K that are potential contraction outcomes. Blocking is represented by a binary relation on the outcome set. If a potential outcome X blocks another potential outcome Y, and X does not imply the sentence p to be contracted, then Y ≠ K ÷ p. The contraction outcome K ÷ p is equal to the (...)
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  • Changes in Preference.Sven Ove Hansson - 1995 - Theory and Decision 38 (1):1-28.
  • Notes on the History of Ideas Behind AGM.Peter Gärdenfors - 2011 - Journal of Philosophical Logic 40 (2):115 - 120.
  • Systematic Withdrawal.Thomas Meyer, Johannes Heidema, Willem Labuschagne & Louise Leenen - 2002 - Journal of Philosophical Logic 31 (5):415-443.
    Although AGM theory contraction (Alchourrón et al., 1985; Alchourrón and Makinson, 1985) occupies a central position in the literature on belief change, there is one aspect about it that has created a fair amount of controversy. It involves the inclusion of the postulate known as Recovery. As a result, a number of alternatives to AGM theory contraction have been proposed that do not always satisfy the Recovery postulate (Levi, 1991, 1998; Hansson and Olsson, 1995; Fermé, 1998; Fermé and Rodriguez, 1998; (...)
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  • How Not to Change the Theory of Theory Change: A Reply to Tennant.Sven Ove Hansson & Hans Rott - 1995 - British Journal for the Philosophy of Science 46 (3):361-380.
    A number of seminal papers on the logic of belief change by Alchourrön, Gärden-fors, and Makinson have given rise to what is now known as the AGM paradigm. The present discussion note is a response to Neil Tennant's [1994], which aims at a critical appraisal of the AGM approach and the introduction of an alternative approach. We show that important parts of Tennants's critical remarks are based on misunderstandings or on lack of information. In the course of doing this, we (...)
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  • Changing the Theory of Theory Change: Reply to My Critics.Neil Tennant - 1997 - British Journal for the Philosophy of Science 48 (4):569-586.
    Changing the Theory of Theory Change: Towards a Computational Approach’ (Tennant [1994]; henceforth CTTC) claimed that the AGM postulate of recovery is false, and that AGM contractions of theories can be more than minimally mutilating. It also described an alternative, computational method for contracting theories, called the Staining Algorithm. Makinson [1995] and Hansson and Rott [1995] criticized CTTC's arguments against AGM-theory, and its specific proposals for an alternative, computational approach. This paper replies as comprehensively as space allows.
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  • Modellings for Belief Change: Prioritization and Entrenchment.Hans Rott - 1992 - Theoria 58 (1):21-57.
    We distinguish the set of explicit beliefs of a reasoner, his "belief base", from the beliefs that are merely implicit. Syntax-based belief change governed by the structure of the belief base and the ranking ("prioritization") of its elements is reconstructed with the help of an epistemic entrenchment relation in the style of Gärdenfors and Makinson. Though priorities are essentially different from entrenchments, distinguished relations of epistemic entrenchment may be obtained from prioritized belief bases by a number of different constructions. An (...)
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  • Preference-Based Belief Revision for Rule-Based Agents.Natasha Alechina, Mark Jago & Brian Logan - 2008 - Synthese 165 (2):159-177.
    Agents which perform inferences on the basis of unreliable information need an ability to revise their beliefs if they discover an inconsistency. Such a belief revision algorithm ideally should be rational, should respect any preference ordering over the agent’s beliefs (removing less preferred beliefs where possible) and should be fast. However, while standard approaches to rational belief revision for classical reasoners allow preferences to be taken into account, they typically have quite high complexity. In this paper, we consider belief revision (...)
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  • Bootstrap Contraction.Sven Ove Hansson - 2013 - Studia Logica 101 (5):1013-1029.
    We can often specify how we would contract by a certain sentence by saying that this contraction would coincide with some other contraction that we know how to perform. We can for instance clarify that our contraction by p&q would coincide with our contraction by p, or by q, or by {p, q}. In a framework where the set of potential outcomes is known, some contractions are “self-evident” in the sense that there is only one serious candidate that can be (...)
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  • Back to Basics: Belief Revision Through Direct Selection.Sven Hansson - 2019 - Studia Logica 107 (5):887-915.
    Traditionally, belief change is modelled as the construction of a belief set that satisfies a success condition. The success condition is usually that a specified sentence should be believed or not believed. Furthermore, most models of belief change employ a select-and-intersect strategy. This means that a selection is made among primary objects that satisfy the success condition, and the intersection of the selected objects is taken as outcome of the operation. However, the select-and-intersect method is difficult to justify, in particular (...)
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  • Maximal and Perimaximal Contraction.Sven Ove Hansson - 2013 - Synthese 190 (16):3325-3348.
    Generalizations of partial meet contraction are introduced that start out from the observation that only some of the logically closed subsets of the original belief set are at all viable as contraction outcomes. Belief contraction should proceed by selection among these viable options. Several contraction operators that are based on such selection mechanisms are introduced and then axiomatically characterized. These constructions are more general than the belief base approach. It is shown that partial meet contraction is exactly characterized by adding (...)
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  • AGM 25 Years: Twenty-Five Years of Research in Belief Change.Eduardo Fermé & Sven Ove Hansson - 2011 - Journal of Philosophical Logic 40 (2):295 - 331.
    The 1985 paper by Carlos Alchourrón (1931–1996), Peter Gärdenfors, and David Makinson (AGM), "On the Logic of Theory Change: Partial Meet Contraction and Revision Functions" was the starting-point of a large and rapidly growing literature that employs formal models in the investigation of changes in belief states and databases. In this review, the first twentyfive years of this development are summarized. The topics covered include equivalent characterizations of AGM operations, extended representations of the belief states, change operators not included in (...)
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  • AGM 25 Years: Twenty-Five Years of Research in Belief Change.Eduardo Fermé & Sven Ove Hansson - 2011 - Journal of Philosophical Logic 40 (2):295-331.
    The 1985 paper by Carlos Alchourrón, Peter Gärdenfors, and David Makinson, “On the Logic of Theory Change: Partial Meet Contraction and Revision Functions” was the starting-point of a large and rapidly growing literature that employs formal models in the investigation of changes in belief states and databases. In this review, the first twenty-five years of this development are summarized. The topics covered include equivalent characterizations of AGM operations, extended representations of the belief states, change operators not included in the original (...)
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  • Coherentist Contraction.SvenOve Hansson - 2000 - Journal of Philosophical Logic 29 (3):315-330.
    A model of coherentist belief contraction is constructed. The outcome of belief contraction is required to be one of the coherent subsets of the original belief set, and a set of plausible properties is proposed for this set of coherent subsets. The contraction operators obtained in this way are shown to coincide with well-known belief base operations. This connection between coherentist and foundationalist approaches to belief change has important implications for the philosophical interpretation of models of belief change.
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  • Changes of Disjunctively Closed Bases.Sven Ove Hansson - 1993 - Journal of Logic, Language and Information 2 (4):255-284.
    An operator of contraction for a belief set (a theory) can be obtained by assigning to it a belief base and an operator of partial meet contraction for that base. It is argued that closure of the base under disjunction is an intuitively reasonable condition. Axiomatic characterizations are given of the contractions of belief sets that can be generated by (various types of) partial meet contraction on disjunctively closed bases. The corresponding revision operators are also characterized. Finally, some results are (...)
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  • Specified Meet Contraction.Sven Ove Hansson - 2008 - Erkenntnis 69 (1):31-54.
    Specified meet contraction is the operation defined by the identity where ∼ is full meet contraction and f is a sentential selector, a function from sentences to sentences. With suitable conditions on the sentential selector, specified meet contraction coincides with the partial meet contractions that yield a finite-based contraction outcome if the original belief set is finite-based. In terms of cognitive realism, specified meet contraction has an advantage over partial meet contraction in that the selection mechanism operates on sentences rather (...)
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  • Belief Liberation.Richard Booth, Samir Chopra, Aditya Ghose & Thomas Meyer - 2005 - Studia Logica 79 (1):47-72.
    We provide a formal study of belief retraction operators that do not necessarily satisfy the postulate. Our intuition is that a rational description of belief change must do justice to cases in which dropping a belief can lead to the inclusion, or ‘liberation’, of others in an agent's corpus. We provide two models of liberation via retraction operators: ρ-liberation and linear liberation. We show that the class of ρ-liberation operators is included in the class of linear ones and provide axiomatic (...)
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  • Coherentist Contraction.Sven Ove Hansson - 2000 - Journal of Philosophical Logic 29 (3):315 - 330.
    A model of coherentist belief contraction is constructed. The outcome of belief contraction is required to be one of the coherent subsets of the original belief set, and a set of plausible properties is proposed for this set of coherent subsets. The contraction operators obtained in this way are shown to coincide with well-known belief base operations. This connection between coherentist and "foundationalist" approaches to belief change has important implications for the philosophical interpretation of models of belief change.
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  • Equilibria in Social Belief Removal.Richard Booth & Thomas Meyer - 2010 - Synthese 177 (1):97 - 123.
    In studies of multi-agent interaction, especially in game theory, the notion of equilibrium often plays a prominent role. A typical scenario for the belief merging problem is one in which several agents pool their beliefs together to form a consistent "group" picture of the world. The aim of this paper is to define and study new notions of equilibria in belief merging. To do so, we assume the agents arrive at consistency via the use of a social belief removal function, (...)
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  • Outcome Level Analysis of Belief Contraction.Sven Ove Hansson - 2013 - Review of Symbolic Logic 6 (2):183-204.
    The outcome set of a belief change operator is the set of outcomes that can be obtained with it. Axiomatic characterizations are reported for the outcome sets of the standard AGM contraction operators and eight types of base-generated contraction. These results throw new light on the properties of some of these operators.
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  • Knowledge Base Dynamics, Abduction, and Database Updates.Chandrabose Aravindan & Phan Minh Dung - 1995 - Journal of Applied Non-Classical Logics 5 (1):51-76.
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  • A Plea for Accuracy.Sven Ove Hansson & Hans Rott - 1998 - Journal of Applied Non-Classical Logics 8 (3):221-224.
    ABSTRACT In his paper ?On Having Bad Contractions, Or: No Room for Recovery? [Te97], N. Tennant attacks the AGM research program of belief revision. We show that he misrepresents the state of affairs in this field of research.
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  • Non Monotonic Reasoning and Belief Revision: Syntactic, Semantic, Foundational and Coherence Approaches.Alvaro del Val - 1997 - Journal of Applied Non-Classical Logics 7 (1-2):213-240.
    ABSTRACT The major approaches to belief revision and non monotonic reasoning proposed in the literature differ along a number of dimensions, including whether they are ?syntax- based? or ?semantic-based?, ?foundational? or ?coherentist?, ?consistence-restoring? or ?inconsistency-tolerant?. Our contribution towards clarifying the connections between these various approaches is threefold: ?We show that the two main approaches to belief revision, the foundations and coherence theories, are mathematically equivalent, thus answering a question left open in [Gar90, Doy92], The distinction between syntax-based approaches to revision (...)
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  • Non Monotonic Reasoning and Belief Revision: Syntactic, Semantic, Foundational and Coherence Approaches.Alvaro del Val - 1997 - Journal of Applied Non-Classical Logics 7 (1-2):213-240.
    ABSTRACT The major approaches to belief revision and non monotonic reasoning proposed in the literature differ along a number of dimensions, including whether they are “syntax- based” or “semantic-based”, “foundational” or “coherentist”, “consistence-restoring” or “inconsistency-tolerant”. Our contribution towards clarifying the connections between these various approaches is threefold: •We show that the two main approaches to belief revision, the foundations and coherence theories, are mathematically equivalent, thus answering a question left open in [Gar90, Doy92], The distinction between syntax-based approaches to revision (...)
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