Results 1  10
of
23
Unreliable Failure Detectors for Reliable Distributed Systems
 Journal of the ACM
, 1996
"... We introduce the concept of unreliable failure detectors and study how they can be used to solve Consensus in asynchronous systems with crash failures. We characterise unreliable failure detectors in terms of two properties — completeness and accuracy. We show that Consensus can be solved even with ..."
Abstract

Cited by 899 (18 self)
 Add to MetaCart
We introduce the concept of unreliable failure detectors and study how they can be used to solve Consensus in asynchronous systems with crash failures. We characterise unreliable failure detectors in terms of two properties — completeness and accuracy. We show that Consensus can be solved even with unreliable failure detectors that make an infinite number of mistakes, and determine which ones can be used to solve Consensus despite any number of crashes, and which ones require a majority of correct processes. We prove that Consensus and Atomic Broadcast are reducible to each other in asynchronous systems with crash failures; thus the above results also apply to Atomic Broadcast. A companion paper shows that one of the failure detectors introduced here is the weakest failure detector for solving Consensus [Chandra et al. 1992].
Reasoning about Information Change
, 1997
"... In this paper, we have combined techniques from epistemic and dynamic logic to arrive at a logic for describing multiagent information change. The key concept of dynamic semantics is that the meaning of an assertion is the way in which the assertion changes the information of the hearer. Thus a dyn ..."
Abstract

Cited by 95 (4 self)
 Add to MetaCart
In this paper, we have combined techniques from epistemic and dynamic logic to arrive at a logic for describing multiagent information change. The key concept of dynamic semantics is that the meaning of an assertion is the way in which the assertion changes the information of the hearer. Thus a dynamic epistemic semantics consist in a explicit formal definition of the information change potential of a sentence. We used these ideas to arrive at the system of Dynamic Epistemic Semantics, which is semantics for a language describing information change in a multiagent setting. This semantics proved useful for analyzing the Muddy Children paradox, and also for giving a semantics for knowledge programs, since it enabled us to model knowledge change by giving an explicit semantics to the triggers of the information change (the latter being the assertions made, or the messages sent). We feel that this is an important extension, since standard approaches to for example the Muddy Children (e.g. Fagin et al. 1995) generally use static epistemic logics like S5 to describe the situation before and after a certain epistemic event, leaving the transition between `before' and `after' to considerations in the metalanguage.
Modelling Knowledge and Action in Distributed Systems
 Distributed Computing
, 1988
"... : We present a formal model that captures the subtle interaction between knowledge and action in distributed systems. We view a distributed system as a set of runs, where a run is a function from time to global states and a global state is a tuple consisting of an environment state and a local state ..."
Abstract

Cited by 85 (28 self)
 Add to MetaCart
: We present a formal model that captures the subtle interaction between knowledge and action in distributed systems. We view a distributed system as a set of runs, where a run is a function from time to global states and a global state is a tuple consisting of an environment state and a local state for each process in the system. This model is a generalization of those used in many previous papers. Actions in this model are associated with functions from global states to global states. A protocol is a function from local states to actions. We extend the standard notion of a protocol by defining knowledgebased protocols, ones in which a process' actions may depend explicitly on its knowledge. Knowledgebased protocols provide a natural way of describing how actions should take place in a distributed system. Finally, we show how the notion of one protocol implementing another can be captured in our model. Some material in this paper appeared in preliminary form in [HF85]. An abridge...
A KnowledgeBased Analysis of Zero Knowledge
, 1988
"... While the intuition underlying a zero knowledge proof system [GMR85] is that no "knowledge" is leaked by the prover to the verifier, researchers are just beginning to analyze such proof systems in terms of formal notions of knowledge. In this paper, we show how interactive proof systems motivate a ..."
Abstract

Cited by 27 (18 self)
 Add to MetaCart
While the intuition underlying a zero knowledge proof system [GMR85] is that no "knowledge" is leaked by the prover to the verifier, researchers are just beginning to analyze such proof systems in terms of formal notions of knowledge. In this paper, we show how interactive proof systems motivate a new notion of practical knowledge, and we capture the definition of an interactive proof system in terms of practical knowledge. Using this notion of knowledge, we formally capture and prove the intuition that the prover does not leak any knowledge of any fact (other than the fact being proven) during a zero knowledge proof. We extend this result to show that the prover does not leak any knowledge of how to compute any information (such as the factorization of a number) during a zero knowledge proof. Finally, we de ne the notion of a weak interactive proof in which the prover is limited to probabilistic, polynomialtime computations, and we prove analogous security results for such proof systems. We showthat, in a precise sense, any nontrivial weak interactive proof must be a proof about the prover's knowledge, and show that, under natural conditions, the notions of interactive proofs of knowledge defined in [TW87] and [FFS87] are instances of weak interactive proofs.
The secret of My Success
 SYNTHESE
, 2004
"... In an information state where various agents have both factual knowledge and knowledge about each other, announcements can be made that change the state of information. Such informative announcements can have the curious property that they become false because they are announced. The most typical ex ..."
Abstract

Cited by 14 (6 self)
 Add to MetaCart
In an information state where various agents have both factual knowledge and knowledge about each other, announcements can be made that change the state of information. Such informative announcements can have the curious property that they become false because they are announced. The most typical example of that is `fact p is true and you don't know that', after which you know that p,which entails the negation of the announcement formula. The announcement of such a formula in a given information state is called an unsuccessful update. A successful formula is a formula that always becomes common knowledge after being announced. Analysis of information systems and `philosophical puzzles' reveals a growing number of dynamic phenomena that can be described or explained by unsuccessful updates. This increases our understanding of such philosophical problems. We also investigate the syntactic characterization of the successful formulas.
Rational interactions in multiagent environments: communication
, 1998
"... We address the issue of rational communicative behavior among autonomous intelligent agents that have to make decisions as to what, to whom, and how to communicate. We treat communicative actions as aimed at increasing the efficiency of interaction among agents. We postulate that a rational speaker ..."
Abstract

Cited by 13 (5 self)
 Add to MetaCart
We address the issue of rational communicative behavior among autonomous intelligent agents that have to make decisions as to what, to whom, and how to communicate. We treat communicative actions as aimed at increasing the efficiency of interaction among agents. We postulate that a rational speaker design a speech act so as to maximally increase the benefit obtained as the result of the interaction. We quantify the gain in the quality of interaction as the expected utility, and we present a framework that allows an agent to compute the expected utility of various communicative actions. Our framework uses the Recursive Modeling Method as the representation of the agent's state of knowledge, including the agent's preferences, abilities and beliefs about the world, as well as the beliefs the agent has about the other agents, the beliefs it has about the other agents ' beliefs, and so on. A decisiontheoretic pragmatics of a communicative act can be then defined as the transformation it induces on the agent's state of knowledge about its decisionmaking situation. This transformation leads to a change in the quality of the interaction, expressed in terms of the benefit to the agent. We analyze decisiontheoretic pragmatics of a number of important communicative acts, and investigate their expected utility using examples.
Knowledge in Multiagent Systems: Initial Configurations and Broadcast
 ACM TRANSACTIONS OF COMPUTATIONAL LOGIC
, 2000
"... ... this paper we study two special cases of this framework: full systems and hypercubes. Both model static situations in which no agent has any information about another agent's state. Full systems and hypercubes are an appropriate model for the initial congurations of many systems of interest. We ..."
Abstract

Cited by 12 (8 self)
 Add to MetaCart
... this paper we study two special cases of this framework: full systems and hypercubes. Both model static situations in which no agent has any information about another agent's state. Full systems and hypercubes are an appropriate model for the initial congurations of many systems of interest. We establish a correspondence between full systems and hypercube systems and certain classes of Kripke frames. We show that these classes of systems correspond to the same logic. Moreover, this logic is also the same as that generated by the larger class of weakly directed frames. We provide a sound and complete axiomatization, S5WDn , of this logic, and study its computational complexity. Finally, we show that under certain natural assumptions, in a model where knowledge evolves over time, S5WDn characterises the properties of knowledge not just at the initial conguration, but also at all later congurations. In particular, this holds for homogeneous broadcast systems, which capture settings in which agents are initially ignorant of each others local states, operate synchronously, have perfect recall, and can communicate only by broadcasting.
Games Computers Play: GameTheoretic Aspects of Computing
 In
, 1992
"... this article is on protocols allowing the wellfunctioning parts of such a large and complex system to carry out their work despite the failure of others. Many deep and interesting results on such problems have been discovered by computer scientists in recent years, the incorporation of which into g ..."
Abstract

Cited by 10 (1 self)
 Add to MetaCart
this article is on protocols allowing the wellfunctioning parts of such a large and complex system to carry out their work despite the failure of others. Many deep and interesting results on such problems have been discovered by computer scientists in recent years, the incorporation of which into game theory can greatly enrich this field
Sum and Product in Dynamic Epistemic Logic
, 2007
"... The SumandProduct riddle was first published in the reference H. Freudenthal (1969, Nieuw Archief voor Wiskunde 3, 152) [6]. We provide an overview on the history of the dissemination of this riddle through the academic and puzzlemath community. This includes some references to precursors of the ..."
Abstract

Cited by 10 (5 self)
 Add to MetaCart
The SumandProduct riddle was first published in the reference H. Freudenthal (1969, Nieuw Archief voor Wiskunde 3, 152) [6]. We provide an overview on the history of the dissemination of this riddle through the academic and puzzlemath community. This includes some references to precursors of the riddle, that were previously (as far as we know) unknown. We then model the SumandProduct riddle in a modal logic called public announcement logic. This logic contains operators for knowledge, but also operators for the informational consequences of public announcements. The logic is interpreted on multiagent Kripke models. The information in the riddle can be represented in the traditional way by number pairs, so that Sum knows their sum and Product their product, but also as an interpreted system, so that Sum and Product at least know their local state. We show that the different representations are isomorphic. We also provide characteristic formulas of the initial epistemic state of the riddle. We analyse one of the announcements towards the solution of the riddle as a socalled unsuccessful update: a formula that becomes false because it is announced. The riddle is then implemented and its solution verified in the epistemic model checker DEMO. This can be done, we think, surprisingly elegantly. The results are compared with other work in epistemic model checking and the complexity is experimentally investigated for several representations and parameter settings.
Unreliable Failure Detectors For Asynchronous Distributed Systems
 in the Proceedings of the 10 th Annual ACM Symposium on Principles of Distributed Computing
, 1993
"... equivalent in asynchronous systems. Thus all our results regarding the solvability of Consensus using failure detectors, apply to Atomic Broadcast as well. The work in this thesis was funded by an IBM graduate fellowship and grants from NSF, DARPA/NASA, the IBM Endicott Programming Laboratory, Siem ..."
Abstract

Cited by 7 (1 self)
 Add to MetaCart
equivalent in asynchronous systems. Thus all our results regarding the solvability of Consensus using failure detectors, apply to Atomic Broadcast as well. The work in this thesis was funded by an IBM graduate fellowship and grants from NSF, DARPA/NASA, the IBM Endicott Programming Laboratory, Siemens Corp and the Natural Siences and Engineering Research Council of Canada. Biographical Sketch Tushar Deepak Chandra was born in New Delhi, India on November 13, 1966. He spent his childhood in various cities in India: Bombay, Calcutta and finally Kanpur. After completing high school at the Doon school, he went on to do a Bachelor of Technology in Computer Science at the Indian Institute of Technology at Kanpur. He joined the graduate program in Computer Science at Cornell University in August 1988. iii This thesis is dedicated to my parents who taught me how to think. iv Acknowledgements A large number of people contributed either directly or i