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Temporal and modal logic
- HANDBOOK OF THEORETICAL COMPUTER SCIENCE
, 1995
"... We give a comprehensive and unifying survey of the theoretical aspects of Temporal and modal logic. ..."
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Cited by 1310 (17 self)
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We give a comprehensive and unifying survey of the theoretical aspects of Temporal and modal logic.
The knowledge complexity of interactive proof systems
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, 1989
"... Usually, a proof of a theorem contains more knowledge than the mere fact that the theorem is true. For instance, to prove that a graph is Hamiltonian it suffices to exhibit a Hamiltonian tour in it; however, this seems to contain more knowledge than the single bit Hamiltonian/non-Hamiltonian. In th ..."
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Cited by 1246 (39 self)
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Usually, a proof of a theorem contains more knowledge than the mere fact that the theorem is true. For instance, to prove that a graph is Hamiltonian it suffices to exhibit a Hamiltonian tour in it; however, this seems to contain more knowledge than the single bit Hamiltonian/non-Hamiltonian. In this paper a computational complexity theory of the "knowledge " contained in a proof is developed. Zero-knowledge proofs are defined as those proofs that convey no additional knowledge other than the correctness of the proposition in question. Examples of zero-knowledge proof systems are given for the languages of quadratic residuosity and quadratic nonresiduosity. These are the first examples of zero-knowledge proofs for languages not known to be efficiently recognizable.
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 ..."
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Cited by 1094 (19 self)
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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].
Towards flexible teamwork
- JOURNAL OF ARTIFICIAL INTELLIGENCE RESEARCH
, 1997
"... Many AI researchers are today striving to build agent teams for complex, dynamic multi-agent domains, with intended applications in arenas such as education, training, entertainment, information integration, and collective robotics. Unfortunately, uncertainties in these complex, dynamic domains obst ..."
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Cited by 570 (59 self)
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Many AI researchers are today striving to build agent teams for complex, dynamic multi-agent domains, with intended applications in arenas such as education, training, entertainment, information integration, and collective robotics. Unfortunately, uncertainties in these complex, dynamic domains obstruct coherent teamwork. In particular, team members often encounter differing, incomplete, and possibly inconsistent views of their environment. Furthermore, team members can unexpectedly fail in fulfilling responsibilities or discover unexpected opportunities. Highly flexible coordination and communication is key in addressing such uncertainties. Simply tting individual agents with precomputed coordination plans will not do, for their in flexibility can cause severe failures in teamwork, and their domain-specificity hinders reusability. Our central hypothesis is that the key to such flexibility and reusability isproviding agents with general models of teamwork. Agents exploit such models to autonomously reason about coordination and communication, providing requisite flexibility. Furthermore, the models enable reuse across domains, both saving implementation effort and enforcing consistency. This article presents one general, implemented model of teamwork, called STEAM. The basic building block of teamwork in STEAM is joint intentions (Cohen & Levesque, 1991b); teamwork in STEAM is based on agents' building up a (partial) hierarchy of joint intentions (this hierarchy is seen to parallel Grosz & Kraus's partial Shared-Plans, 1996). Furthermore, in STEAM, team members monitor the team's and individual members' performance, reorganizing the team as necessary. Finally, decision-theoretic communication selectivity in STEAM ensures reduction in communication overheads of teamwork, with appropriate sensitivity to the environmental conditions. This article describes STEAM's application in three different complex domains, and presents detailed empirical results.
Formalising trust as a computational concept
, 1994
"... Trust is a judgement of unquestionable utility — as humans we use it every day of our lives. However, trust has suffered from an imperfect understanding, a plethora of definitions, and informal use in the literature and in everyday life. It is common to say “I trust you, ” but what does that mean? T ..."
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Cited by 529 (6 self)
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Trust is a judgement of unquestionable utility — as humans we use it every day of our lives. However, trust has suffered from an imperfect understanding, a plethora of definitions, and informal use in the literature and in everyday life. It is common to say “I trust you, ” but what does that mean? This thesis provides a clarification of trust. We present a formalism for trust which provides us with a tool for precise discussion. The formalism is implementable: it can be embedded in an artificial agent, enabling the agent to make trust-based decisions. Its applicability in the domain of Distributed Artificial Intelligence (DAI) is raised. The thesis presents a testbed populated by simple trusting agents which substantiates the utility of the formalism. The formalism provides a step in the direction of a proper understanding and definition of human trust. A contribution of the thesis is its detailed exploration of the possibilities of future work in the area. Summary 1. Overview This thesis presents an overview of trust as a social phenomenon and discusses it formally. It argues that trust is: • A means for understanding and adapting to the complexity of the environment. • A means of providing added robustness to independent agents. • A useful judgement in the light of experience of the behaviour of others. • Applicable to inanimate others. The thesis argues these points from the point of view of artificial agents. Trust in an artificial agent is a means of providing an additional tool for the consideration of other agents and the environment in which it exists. Moreover, a formalisation of trust enables the embedding of the concept into an artificial agent. This has been done, and is documented in the thesis. 2. Exposition There are places in the thesis where it is necessary to give a broad outline before going deeper. In consequence it may seem that the subject is not receiving a thorough treatment, or that too much is being discussed at one time! (This is particularly apparent in the first and second chapters.) To present a thorough understanding of trust, we have proceeded breadth first in the introductory chapters. Chapter 3 expands, depth first, presenting critical views of established researchers.
Controlling Cooperative Problem Solving in Industrial Multi-Agent Systems using Joint Intentions
- ARTIFICIAL INTELLIGENCE JOURNAL
, 1995
"... One reason why Distributed AI (DAI) technology has been deployed in relatively few real-size applications is that it lacks a clear and implementable model of cooperative problem solving which specifies how agents should operate and interact in complex, dynamic and unpredictable environments. As a co ..."
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Cited by 331 (36 self)
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One reason why Distributed AI (DAI) technology has been deployed in relatively few real-size applications is that it lacks a clear and implementable model of cooperative problem solving which specifies how agents should operate and interact in complex, dynamic and unpredictable environments. As a consequence of the experience gained whilst building a number of DAI systems for industrial applications, a new principled model of cooperation has been developed. This model, called Joint Responsibility, has the notion of joint intentions at its core. It specifies pre-conditions which must be attained before collaboration can commence and prescribes how individuals should behave both when joint activity is progressing satisfactorily and also when it runs into difficulty. The theoretical model has been used to guide the implementation of a general-purpose cooperation framework and the qualitative and quantitative benefits of this implementation have been assessed through a series of comparativ...
Reaching agreements through argumentation: a logical model and implementation
- ARTIFICIAL INTELLIGENCE
, 1998
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Agent-Oriented Software Engineering
, 1999
"... Software and knowledge... In this article, we argue that intelligent agents and agent-based systems offer novel opportunities for developing effective tools and techniques. Following a discussion on the classic subject of what makes software complex, we introduce intelligent agents as software struc ..."
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Cited by 259 (19 self)
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Software and knowledge... In this article, we argue that intelligent agents and agent-based systems offer novel opportunities for developing effective tools and techniques. Following a discussion on the classic subject of what makes software complex, we introduce intelligent agents as software structures capable of making "rational decisions". Such rational decision-makers are well-suited to the construction of certain types of software, which mainstream software engineering has had little success with. We then go on to examine a number of prototype techniques proposed for engineering agent systems, including formal specification and verification methods for agent systems, and techniques for implementing agent specifications
The Transis Approach to High Availability Cluster Communication
- Communications of the ACM
, 1996
"... Introduction In the local elections system of the municipality of "Wiredville" 1 , several computers were used to establish an electronic town hall. The computers were linked by a network. When an issue was put to a vote, voters could manually feed their votes into any of the computers, ..."
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Cited by 252 (14 self)
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Introduction In the local elections system of the municipality of "Wiredville" 1 , several computers were used to establish an electronic town hall. The computers were linked by a network. When an issue was put to a vote, voters could manually feed their votes into any of the computers, which replicated the updates to all of the other computers. Whenever the current tally was desired, any computer could be used to supply an up-to-the-moment count. On the night of an important election, a room with one of the computers became crowded with lobbyists and politicians. Unexpectedly, someone accidentally stepped on the network wire, cutting communication between two parts of the network. The vote counting stopped until the network was repaired, and the entire tally had to be restarted from scratch. This would not have happened if the vote-counting system had been built with partitions in mind. After the unexpected severance, vote counting could have continued at all t
Reasoning about Belief in Cryptographic Protocols
- Proceedings 1990 IEEE Symposium on Research in Security and Privacy
, 1990
"... Abstract. Analysis methods for cryptographic protocols have often focused on information leakage rather than on seeing whether a protocol meets its goals. Many protocols, however, fall far short of meeting their goals, sometimes for quite subtle reasons. We introduce a mechanism for reasoning about ..."
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Cited by 222 (6 self)
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Abstract. Analysis methods for cryptographic protocols have often focused on information leakage rather than on seeing whether a protocol meets its goals. Many protocols, however, fall far short of meeting their goals, sometimes for quite subtle reasons. We introduce a mechanism for reasoning about belief as a systematic way to understand the working of cryptographic protocols. Our mechanism captures more features of such protocols than that given in a recent work [1], to which our proposals are a substantial extension. 1 Introduction Solutions to computer security problems over the last few years have brought forth the need for rigorous analysis methods. Formal tools must be provided to determine whether a solution indeed solves a problem, as well as to enable comparisons between proposed solutions. In this paper we propose a method for reasoning about cryptographic protocols in a distributed environment. The work described was inspired by the recent development of a modal logic to ...
