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37
Alternatingtime Temporal Logic
 Journal of the ACM
, 1997
"... Temporal logic comes in two varieties: lineartime temporal logic assumes implicit universal quantification over all paths that are generated by system moves; branchingtime temporal logic allows explicit existential and universal quantification over all paths. We introduce a third, more general var ..."
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Cited by 444 (47 self)
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Temporal logic comes in two varieties: lineartime temporal logic assumes implicit universal quantification over all paths that are generated by system moves; branchingtime temporal logic allows explicit existential and universal quantification over all paths. We introduce a third, more general variety of temporal logic: alternatingtime temporal logic offers selective quantification over those paths that are possible outcomes of games, such as the game in which the system and the environment alternate moves. While lineartime and branchingtime logics are natural specification languages for closed systems, alternatingtime logics are natural specification languages for open systems. For example, by preceding the temporal operator "eventually" with a selective path quantifier, we can specify that in the game between the system and the environment, the system has a strategy to reach a certain state. Also the problems of receptiveness, realizability, and controllability can be formulated as modelchecking problems for alternatingtime formulas.
The Complexity of Decentralized Control of Markov Decision Processes
 Mathematics of Operations Research
, 2000
"... We consider decentralized control of Markov decision processes and give complexity bounds on the worstcase running time for algorithms that find optimal solutions. Generalizations of both the fullyobservable case and the partiallyobservable case that allow for decentralized control are described. ..."
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Cited by 285 (46 self)
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We consider decentralized control of Markov decision processes and give complexity bounds on the worstcase running time for algorithms that find optimal solutions. Generalizations of both the fullyobservable case and the partiallyobservable case that allow for decentralized control are described. For even two agents, the finitehorizon problems corresponding to both of these models are hard for nondeterministic exponential time. These complexity results illustrate a fundamental difference between centralized and decentralized control of Markov decision processes. In contrast to the problems involving centralized control, the problems we consider provably do not admit polynomialtime algorithms. Furthermore, assuming EXP NEXP, the problems require superexponential time to solve in the worst case.
The NPcompleteness column: an ongoing guide
 Journal of Algorithms
, 1985
"... This is the nineteenth edition of a (usually) quarterly column that covers new developments in the theory of NPcompleteness. The presentation is modeled on that used by M. R. Garey and myself in our book ‘‘Computers and Intractability: A Guide to the Theory of NPCompleteness,’ ’ W. H. Freeman & Co ..."
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Cited by 188 (0 self)
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This is the nineteenth edition of a (usually) quarterly column that covers new developments in the theory of NPcompleteness. The presentation is modeled on that used by M. R. Garey and myself in our book ‘‘Computers and Intractability: A Guide to the Theory of NPCompleteness,’ ’ W. H. Freeman & Co., New York, 1979 (hereinafter referred to as ‘‘[G&J]’’; previous columns will be referred to by their dates). A background equivalent to that provided by [G&J] is assumed, and, when appropriate, crossreferences will be given to that book and the list of problems (NPcomplete and harder) presented there. Readers who have results they would like mentioned (NPhardness, PSPACEhardness, polynomialtimesolvability, etc.) or open problems they would like publicized, should
On the complexity of space bounded interactive proofs
 In 30th Annual Symposium on Foundations of Computer Science
, 1989
"... Some of the most exciting developments in complexity theory in recent years concern the complexity of interactive proof systems, defined by Goldwasser, Micali and Rackoff (1985) and independently by Babai (1985). In this paper, we survey results on the complexity of space bounded interactive proof s ..."
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Cited by 54 (5 self)
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Some of the most exciting developments in complexity theory in recent years concern the complexity of interactive proof systems, defined by Goldwasser, Micali and Rackoff (1985) and independently by Babai (1985). In this paper, we survey results on the complexity of space bounded interactive proof systems
Synthesizing Distributed Systems
, 2001
"... In system synthesis, we transform a specication into a system that is guaranteed to satisfy the speci cation. When the system is distributed, the goal is to construct the system's underlying processes. Results on multiplayer games imply that the synthesis problem for linear specications is undecid ..."
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Cited by 42 (1 self)
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In system synthesis, we transform a specication into a system that is guaranteed to satisfy the speci cation. When the system is distributed, the goal is to construct the system's underlying processes. Results on multiplayer games imply that the synthesis problem for linear specications is undecidable for general architectures, and is nonelementary decidable for hierarchical architectures, where the processes are linearly ordered and information among them ows in one direction. In this paper we present a signicant extension of this result. We handle both linear and branching specications, and we show that a sucient condition for decidability of the synthesis problem is a linear or cyclic order among the processes, in which information ows in either one or both directions. We also allow the processes to have internal hidden variables, and we consider communications with and without delay. Many practical applications fall into this class. 1 Introduction In system synthesis, we...
Distributed Controller Synthesis for Local Specifications
, 2001
"... We consider the problem of synthesizing distributed controllers for reactive systems against local specifications. We show that a larger class of architectures become decidable in comparison to the analogous problem for global specifications. We identify the exact class of architectures for which th ..."
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Cited by 23 (3 self)
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We consider the problem of synthesizing distributed controllers for reactive systems against local specifications. We show that a larger class of architectures become decidable in comparison to the analogous problem for global specifications. We identify the exact class of architectures for which the problem is decidable. Our results also show the decidability of a related realizability problem for local specifications.
Common Knowledge and Update in Finite Environments
 Information and Computation
, 1997
"... Logics of knowledge have been shown to provide a useful approach to the high level specification and analysis of distributed systems. It has been proposed that such systems can be developed using knowledgebased protocols, in which agents' actions have preconditions that test their state of knowledg ..."
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Cited by 20 (5 self)
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Logics of knowledge have been shown to provide a useful approach to the high level specification and analysis of distributed systems. It has been proposed that such systems can be developed using knowledgebased protocols, in which agents' actions have preconditions that test their state of knowledge. Both computerassisted analysis of the knowledge properties of systems and automated compilation of knowledgebased protocols require the development of algorithms for the computation of states of knowledge. This paper studies one of the computational problems of interest, the model checking problem for knowledge formulae in the S5 n Kripke structures generated by finite state environments in which states determine an observation for each agent. Agents are assumed to have perfect recall, and may operate synchronously or asynchronously. It is shown that, in this setting, model checking of common knowledge formulae is intractable, but efficient incremental algorithms are developed for formu...
ComplexityTheoretic Aspects of Interactive Proof Systems
, 1989
"... In 1985, Goldwasser, Micali and Rackoff formulated interactive proof systems as a tool for developing cryptographic protocols. Indeed, many exciting cryptographic results followed from studying interactive proof systems and the related concept of zeroknowledge. Interactive proof systems also have a ..."
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Cited by 19 (3 self)
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In 1985, Goldwasser, Micali and Rackoff formulated interactive proof systems as a tool for developing cryptographic protocols. Indeed, many exciting cryptographic results followed from studying interactive proof systems and the related concept of zeroknowledge. Interactive proof systems also have an important part in complexity theory merging the well established concepts of probabilistic and nondeterministic computation. This thesis will study the complexity of various models of interactive proof systems. A perfect zeroknowledge interactive protocol convinces a verifier that a string is in a language without revealing any additional knowledge in an information theoretic sense. This thesis will show that for any language that has a perfect zeroknowledge proof system, its complement has a short interactive protocol. This result implies that there are not any perfect zeroknowledge protocols for NPcomplete languages unless the polynomialtime hierarchy collapses. Thus knowledge comp...
Email and the unexpected power of interaction
 Structure in Complexity theory
, 1988
"... This is a true fable about Merlin, the infinitely intelligent but never trusted magician; and Arthur, the reasonable but impatient sovereign with an occasional unorthodox request; about the concept of an efficient proof; about polynomials and interpolation, electronic mail, coin flipping, and the in ..."
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Cited by 18 (3 self)
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This is a true fable about Merlin, the infinitely intelligent but never trusted magician; and Arthur, the reasonable but impatient sovereign with an occasional unorthodox request; about the concept of an efficient proof; about polynomials and interpolation, electronic mail, coin flipping, and the incredible power of interaction. About MIP, IP, #P, P SP ACE, NEXP T IME, and new techniques that do not relativize. About fast progress, fierce competition, and email ethics. 1 How did Merlin end up in the cave? In the court of King Arthur1 there lived 150 knights and 150 ladies. “Why not 150 married couples, ” the King contemplated one rainy afternoon, and action followed the thought. He asked the Royal Secret Agent (RSA) to draw up a diagram with all the 300 names, indicating bonds of mutual interest between lady and knight by a red line; and the lack thereof, by a blue line. The diagram, with its 1502 = 22, 500 colored lines, looked somewhat confusing, yet it should not confuse Merlin, the court magician, to whom it was subsequently presented by Arthur with the express order to find a perfect matching consisting exclusively of red lines. Merlin walked away, looked at the diagram, and, with his unlimited intellectual ability, immediately recognized that none of the 150! possibilities gave an allred perfect matching. He quickly completed the 150! diagrams, highlighting the wrong blue line in
A decidable class of asynchronous distributed controllers
 In Proc. CONCUR’02, LNCS 2421
, 2002
"... Abstract. We study the problem of synthesizing controllers in a natural distributed asynchronous setting: a finite set of plants interact with their local environments and communicate with each other by synchronizing on common actions. The controllersynthesis problem is to come up with a local stra ..."
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Cited by 16 (1 self)
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Abstract. We study the problem of synthesizing controllers in a natural distributed asynchronous setting: a finite set of plants interact with their local environments and communicate with each other by synchronizing on common actions. The controllersynthesis problem is to come up with a local strategy for each plant such that the controlled behaviour of the network meets a specification. We consider linear time specifications and provide, in some sense, a minimal set of restrictions under which this problem is effectively solvable: we show that the controllersynthesis problem under these restrictions is decidable while the problem becomes undecidable if any one or more of these three restrictions are dropped. 1