1,479 research outputs found
A New Rational Algorithm for View Updating in Relational Databases
The dynamics of belief and knowledge is one of the major components of any
autonomous system that should be able to incorporate new pieces of information.
In order to apply the rationality result of belief dynamics theory to various
practical problems, it should be generalized in two respects: first it should
allow a certain part of belief to be declared as immutable; and second, the
belief state need not be deductively closed. Such a generalization of belief
dynamics, referred to as base dynamics, is presented in this paper, along with
the concept of a generalized revision algorithm for knowledge bases (Horn or
Horn logic with stratified negation). We show that knowledge base dynamics has
an interesting connection with kernel change via hitting set and abduction. In
this paper, we show how techniques from disjunctive logic programming can be
used for efficient (deductive) database updates. The key idea is to transform
the given database together with the update request into a disjunctive
(datalog) logic program and apply disjunctive techniques (such as minimal model
reasoning) to solve the original update problem. The approach extends and
integrates standard techniques for efficient query answering and integrity
checking. The generation of a hitting set is carried out through a hyper
tableaux calculus and magic set that is focused on the goal of minimality.Comment: arXiv admin note: substantial text overlap with arXiv:1301.515
Tableau-based decision procedure for the multi-agent epistemic logic with operators of common and distributed knowledge
We develop an incremental-tableau-based decision procedure for the
multi-agent epistemic logic MAEL(CD) (aka S5_n (CD)), whose language contains
operators of individual knowledge for a finite set Ag of agents, as well as
operators of distributed and common knowledge among all agents in Ag. Our
tableau procedure works in (deterministic) exponential time, thus establishing
an upper bound for MAEL(CD)-satisfiability that matches the (implicit)
lower-bound known from earlier results, which implies ExpTime-completeness of
MAEL(CD)-satisfiability. Therefore, our procedure provides a complexity-optimal
algorithm for checking MAEL(CD)-satisfiability, which, however, in most cases
is much more efficient. We prove soundness and completeness of the procedure,
and illustrate it with an example.Comment: To appear in the Proceedings of the 6th IEEE Conference on Software
Engineering and Formal Methods (SEFM 2008
A Fibred Tableau Calculus for Modal Logics of Agents
In previous works we showed how to combine propositional multimodal logics using Gabbay's \emph{fibring} methodology. In this paper we extend the above mentioned works by providing a tableau-based proof technique for the combined/fibred logics. To achieve this end we first make a comparison between two types of tableau proof systems, (\emph{graph} \emph{path}), with the help of a scenario (The Friend's Puzzle). Having done that we show how to uniformly construct a tableau calculus for the combined logic using Governatori's labelled tableau system \KEM. We conclude with a discussion on \KEM's features
Modal tableaux for verifying stream authentication protocols
To develop theories to specify and reason about various aspects of multi-agent systems, many researchers have proposed the use of modal logics such as belief logics, logics of knowledge, and logics of norms. As multi-agent systems operate in dynamic environments, there is also a need to model the evolution of multi-agent systems through time. In order to introduce a temporal dimension to a belief logic, we combine it with a linear-time temporal logic using a powerful technique called fibring for combining logics. We describe a labelled modal tableaux system for the resulting fibred belief logic (FL) which can be used to automatically verify correctness of inter-agent stream authentication protocols. With the resulting fibred belief logic and its associated modal tableaux, one is able to build theories of trust for the description of, and reasoning about, multi-agent systems operating in dynamic environments
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