476,911 research outputs found
Bisimulation and expressivity for conditional belief, degrees of belief, and safe belief
Plausibility models are Kripke models that agents use to reason about
knowledge and belief, both of themselves and of each other. Such models are
used to interpret the notions of conditional belief, degrees of belief, and
safe belief. The logic of conditional belief contains that modality and also
the knowledge modality, and similarly for the logic of degrees of belief and
the logic of safe belief. With respect to these logics, plausibility models may
contain too much information. A proper notion of bisimulation is required that
characterises them. We define that notion of bisimulation and prove the
required characterisations: on the class of image-finite and preimage-finite
models (with respect to the plausibility relation), two pointed Kripke models
are modally equivalent in either of the three logics, if and only if they are
bisimilar. As a result, the information content of such a model can be
similarly expressed in the logic of conditional belief, or the logic of degrees
of belief, or that of safe belief. This, we found a surprising result. Still,
that does not mean that the logics are equally expressive: the logics of
conditional and degrees of belief are incomparable, the logics of degrees of
belief and safe belief are incomparable, while the logic of safe belief is more
expressive than the logic of conditional belief. In view of the result on
bisimulation characterisation, this is an equally surprising result. We hope
our insights may contribute to the growing community of formal epistemology and
on the relation between qualitative and quantitative modelling
Axiomatization of the AGM theory of belief revision in a temporal logic
It is natural to think of belief revision as the interaction of belief
and information over time. Thus branching-time temporal logic seems a natural
setting for a theory of belief revision. We propose two extensions of a
modal logic that, besides the ""next-time"" temporal operator, contains a
belief operator and an information operator. The first logic is shown to
provide an axiomatization of the first six postulates of the AGM theory
of belief revision, while the second, stronger, logic provides an axiomatization
of the full set of AGM postulates.Belief revision, information, temporal logic, AGM theory
Four Logics for Minimal Belief Revision
It is natural to think of belief revision as the interaction of belief and information over time. Thus branching-time temporal logic seems a natural setting for a theory of belief revision. We propose a logic based on three modal operators: a belief operator, an information operator and a next-time operator. Four logics of increasing strength are proposed. The first is a logic that captures the most basic notion of minimal belief revision. The second characterizes the qualitative content of Bayes' rule. The third provides an axiomatization of the AGM theory of belief revision and the fourth provides a characterization of the notion of plausibility ordering of the set of possible worlds.
Belief change in branching time: AGM-consistency and iterated revision
We study belief change branching-time structures. First, we identify a property of branching-time frames that is equivalent to AGM-consistency, which is defined as follows. A frame is AGM-consistent if the partial belief revision function associated with an arbitrary state-instant pair and an arbitrary model based on that frame can be extended to a full belief revision function that satisfies the AGM postulates. Second, we provide a set of modal axioms that characterize the class of AGM-consistent frames within the modal logic introduced in [Bonanno, Axiomatic characterization of the AGM theory of belief revision in a temporal logic, Artificial Intelligence, 2007]. Third, we introduce a generalization of AGM belief revision functions that allows a clear statement of principles of iterated belief revision and discuss iterated revision both semantically and syntactically.iterated belief revision, branching time, information, belief, modal logic, AGM belief revision
A formal analysis of the notion of preference between deductive arguments
In the last two decades, justification logic has addressed the problem of
including justifications into the field of epistemic logic. Nevertheless,
there is something that has not received enough attention yet: how
epistemic agents might prefer certain justifications to others, in order to
have better pieces of evidence to support a particular belief. In this
work, we study the notion of preference between a particular kind of
justifications: deductive arguments. For doing so, we have built a logic
using tools from epistemic logic, justification logic and logics for belief
dependence. According to our solution, the preferences of an epistemic
agent between different deductive arguments can be reduced to other notions
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