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Physical symbol systems
 Cogn. Sci
"... to review the basis of common understanding between the various disciplines. In my estimate, the most fundamental contribution so far of artificial intelligence and computer science to the joint enterprise of cognitive science has been the notion of a physical symbol system, i.e., the concept of D b ..."
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Cited by 223 (1 self)
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to review the basis of common understanding between the various disciplines. In my estimate, the most fundamental contribution so far of artificial intelligence and computer science to the joint enterprise of cognitive science has been the notion of a physical symbol system, i.e., the concept of D broad class of systems capable of having and manipulating symbois, yet realizable in the physical universe. The notion of symbol so defined is internal to this concept, so it becomes a hypothesis that this notion of symbols includes the symbols that we humans use every day of our lives. In this paper we attempt systematically, but plainly, to lay out the nature of physical symbol systems. Such IJ review is in ways familiar, but not thereby useless. Restatement of fundamentals is an important exercise. 1.
Belief, awareness, and limited reasoning
 ARTIFICIAL INTELLIGENCE
, 1988
"... Several new logics for belief and knowledge are introduced and studied, all of which have the property that agents are not logically omniscient. In particular, in these logics, the set of beliefs of an agent does not necessarily contain all valid formulas. Thus, these logics are more suitable than t ..."
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Cited by 129 (12 self)
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Several new logics for belief and knowledge are introduced and studied, all of which have the property that agents are not logically omniscient. In particular, in these logics, the set of beliefs of an agent does not necessarily contain all valid formulas. Thus, these logics are more suitable than traditional logics for modelling beliefs of humans (or machines) with limited reasoning capabilities. Our first logic is essentially an extension of Levesque's logic of implicit and explicit belief, where we extend to allow multiple agents and higherlevel belief (i.e., beliefs about beliefs). Our second logic deals explicitly with "awareness," where, roughly speaking, it is necessary to be aware of a concept before one can have beliefs about it. Our third logic gives a model of "local reasoning," where an agent is viewed as a "society of minds," each with its own cluster of beliefs, which may contradict each other.
What Can Machines Know? On the Properties of Knowledge in Distributed Systems
 Journal of the ACM
, 1996
"... It has been argued that knowledge is a useful tool for designing and analyzing complex systems. The notion of knowledge that seems most relevant in this context is an external, informationbased notion that can be shown to satisfy all the axioms of the modal logic S5. We carefully examine the pro ..."
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Cited by 51 (9 self)
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It has been argued that knowledge is a useful tool for designing and analyzing complex systems. The notion of knowledge that seems most relevant in this context is an external, informationbased notion that can be shown to satisfy all the axioms of the modal logic S5. We carefully examine the properties of this notion of knowledge and show that they depend crucially, and in subtle ways, on assumptions we make about the system and about the language used for describing knowledge. We present a formal model in which we can capture various assumptions frequently made about systems, such as whether they are deterministic or nondeterministic, whether knowledge is cumulative (which means that processes never "forget"), and whether or not the "environment" affects the state transitions of the processes. We then show that under some assumptions about the system and the language, certain states of knowledge are not attainable and the axioms of S5 do not completely characterize the pr...
Ignoring ignorance and agreeing to disagree
 J. of Economic Theory
, 1990
"... A model of information structure and common knowledge is presented which does not take states of the world as primitive. Rather, these states are constructed as sets of propositions, including propositions which describe knowledge. In this model information structure and measurability structure are ..."
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Cited by 33 (3 self)
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A model of information structure and common knowledge is presented which does not take states of the world as primitive. Rather, these states are constructed as sets of propositions, including propositions which describe knowledge. In this model information structure and measurability structure are endogenously defined in terms of the relation between the propositions. In particular, when agents are ignorant of their own ignorance, the information structure is not a partition of the state space. We show that Aumann’s (Ann. Statist. 4 (1976), 12361239) famous result on the impossibility of agreeing to disagree, which was proved for partitions, can be extended to such information structures. Journal of Economic Literature Classification Numbers: 021, 026. 0 1990 Academic press, hc. 1.
The logic of belief and belief change: A decision theoretic approach
 Journal of Economic Theory
, 1996
"... showed how properties of a decision maker's probabilistic beliefs can be deduced from primitive consistency axioms on preferences. This paper extends that approach and shows how logical properties of belief which underlie economists ' models of information and knowledge can be related to p ..."
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Cited by 18 (0 self)
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showed how properties of a decision maker's probabilistic beliefs can be deduced from primitive consistency axioms on preferences. This paper extends that approach and shows how logical properties of belief which underlie economists ' models of information and knowledge can be related to properties of preferences. Journal of
Analytic tableau systems and interpolation for the modal logics
 KB, KDB, K5, KD5. Studia Logica
"... Abstract. We give complete sequentlike tableau systems for the modal logics KB, KDB, K 5, and KD5. Analytic cut rules are used to obtain the completeness. Our systems have the analytic superformula property and can thus give a decision procedure. Using the systems, we prove the Craig interpolation ..."
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Cited by 12 (10 self)
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Abstract. We give complete sequentlike tableau systems for the modal logics KB, KDB, K 5, and KD5. Analytic cut rules are used to obtain the completeness. Our systems have the analytic superformula property and can thus give a decision procedure. Using the systems, we prove the Craig interpolation lemma for the mentioned logics. 1
The Modal Query Language MDatalog
, 2001
"... We propose a modal query language called MDatalog. A rule of an MDatalog program is a universally quantified modal Horn clause. This language is interpreted in fixeddomain firstorder modal logics over signatures without functions. We give algorithms to construct the least models for MDatalog progr ..."
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Cited by 10 (9 self)
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We propose a modal query language called MDatalog. A rule of an MDatalog program is a universally quantified modal Horn clause. This language is interpreted in fixeddomain firstorder modal logics over signatures without functions. We give algorithms to construct the least models for MDatalog programs. We show PTIME complexity of computing queries for a given MDatalog program in the logics KD, T , KB, KDB, B, K5, KD5, K45, KD45, KB5, and S5, provided that the quantifier depths of queries and the program are finitely bounded, and that the modal depth of the program is finitely bounded in the case when the considered logic is not an extension of K5. Some examples are given to illustrate application of the techniques to reason about belief and knowledge.
Generation of PolicyRich Websites From Declarative Models
, 2009
"... Protecting sensitive data stored behind online websites is a major challenge, but existing techniques are inadequate. Automated website builders typically offer very limited options for specifying custom access policies. Manually adding access policy checks to website code is tedious and errorprone ..."
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Cited by 3 (0 self)
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Protecting sensitive data stored behind online websites is a major challenge, but existing techniques are inadequate. Automated website builders typically offer very limited options for specifying custom access policies. Manually adding access policy checks to website code is tedious and errorprone, and it is currently not feasible to automatically verify that a website conforms to its required access policy. Furthermore, policies change over time, and it can be costly to modify an existing website to reflect the changes or to certify that the modified website still complies with the desired policy. This research presents a declarative modeling approach designed to address these issues, where the data model and the access policy are specified using Alloy, and the Weballoy tool automatically generates a dynamic website that guarantees the access policy by construction. Thesis Supervisor: Daniel Jackson Title: ProfessorAcknowledgments
Decidability Extracted: SYNTHESIZING “CORRECTBYCONSTRUCTION” DECISION PROCEDURES FROM CONSTRUCTIVE PROOFS
, 1998
"... The topic of this thesis is the extraction of efficient and readable programs from formal constructive proofs of decidability. The proof methods employed to generate the efficient code are new and result in clean and readable Nuprl extracts for two nontrivial programs. They are based on the use of ..."
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Cited by 3 (0 self)
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The topic of this thesis is the extraction of efficient and readable programs from formal constructive proofs of decidability. The proof methods employed to generate the efficient code are new and result in clean and readable Nuprl extracts for two nontrivial programs. They are based on the use of Nuprl’s set type and techniques for extracting efficient programs from induction principles. The constructive formal theories required to express the decidability theorems are of independent interest. They formally circumscribe the mathematical knowledge needed to understand the derived algorithms. The formal theories express concepts that are taught at the senior college level. The decidability proofs themselves, depending on this material, are of interest and are presented in some detail. The proof of decidability of classical propositional logic is relative to a semantics based on Kleene’s strong threevalued logic. The constructive proof of intuitionistic decidability presented here is the first machine formalization of this proof. Theexposition reveals aspects of the Nuprl tactic collection relevant to the creation of readable proofs; clear extracts and efficient code are illustrated in the discussion of the proofs.