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11
Roadmap of Infinite Results
, 2008
"... This paper provides a comprehensive summary of equivalence checking results for infinitestate systems. References to the relevant papers will be updated continuously according to the development in the area. The most recent version of this document is available from the webpage ..."
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Cited by 19 (0 self)
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This paper provides a comprehensive summary of equivalence checking results for infinitestate systems. References to the relevant papers will be updated continuously according to the development in the area. The most recent version of this document is available from the webpage
Decidability of Bisimilarity for OneCounter Processes
, 1997
"... It is shown that bisimulation equivalence is decidable for the processes generated by (nondeterministic) pushdown automata where the pushdown behaves like a counter. Also finiteness up to bisimilarity is shown to be decidable for the mentioned processes. ..."
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Cited by 15 (1 self)
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It is shown that bisimulation equivalence is decidable for the processes generated by (nondeterministic) pushdown automata where the pushdown behaves like a counter. Also finiteness up to bisimilarity is shown to be decidable for the mentioned processes.
On the Complexity of Bisimulation Problems for Pushdown Automata
 In Proceedings of IFIP TCS’2000, volume 1872 of LNCS
, 2000
"... All bisimulation problems for pushdown automata are at least PSPACEhard. In particular, we show that (1) Weak bisimilarity of pushdown automata and finite automata is PSPACEhard, even for a small fixed finite automaton, (2) Strong bisimilarity of pushdown automata and finite automata is PSPACEhar ..."
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Cited by 15 (7 self)
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All bisimulation problems for pushdown automata are at least PSPACEhard. In particular, we show that (1) Weak bisimilarity of pushdown automata and finite automata is PSPACEhard, even for a small fixed finite automaton, (2) Strong bisimilarity of pushdown automata and finite automata is PSPACEhard, but polynomial for every fixed finite automaton, (3) Regularity (finiteness) of pushdown automata w.r.t. weak and strong bisimilarity is PSPACEhard.
Undecidability of weak bisimilarity for PAprocesses
 In Proceedings of the 6th International Conference on Developments in Laguage Theory (DLT’02), volume 2450 of LNCS
, 2003
"... Abstract. We prove that the problem whether two PAprocesses are weakly bisimilar is undecidable. We combine several proof techniques to provide a reduction from Post's correspondence problem to our problem: existential quantification technique, masking technique and deadlock elimination techn ..."
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Abstract. We prove that the problem whether two PAprocesses are weakly bisimilar is undecidable. We combine several proof techniques to provide a reduction from Post's correspondence problem to our problem: existential quantification technique, masking technique and deadlock elimination technique.
On the Complexity of Bisimulation Problems for Basic Parallel Processes
 In Proc. of ICALP'2000, volume ? of LNCS
, 2000
"... Strong bisimilarity of Basic Parallel Processes (BPP) is decidable, but the best known algorithm has nonelementary complexity [7]. On the other hand, no lower bound for the problem was known. We show that strong bisimilarity of BPP is coNPhard. Weak bisimilarity of BPP is not known to be decidabl ..."
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Cited by 6 (1 self)
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Strong bisimilarity of Basic Parallel Processes (BPP) is decidable, but the best known algorithm has nonelementary complexity [7]. On the other hand, no lower bound for the problem was known. We show that strong bisimilarity of BPP is coNPhard. Weak bisimilarity of BPP is not known to be decidable, but an NP lower bound has been shown in [31]. We improve this result by showing that weak bisimilarity of BPP is \Pi p 2 hard. Finally, we show that the problems if a BPP is regular (i.e., finite) w.r.t. strong and weak bisimilarity are coNPhard and \Pi p 2 hard, respectively.
Simulation is Decidable for Onecounter Nets (Extended Abstract)
 In Proceedings of CONCUR'98, Lecture Notes in Computer Science 1466:253268
, 1998
"... ) Parosh Aziz Abdulla Dept. of Computer Systems P.O. Box 325 S751 05 Uppsala, Sweden parosh@docs.uu.se Karlis Cerans Institute of Mathematics and Computer Science University of Latvia karlis@cclu.lv Abstract We prove that the simulation preorder is decidable for the class of onecounter nets. ..."
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) Parosh Aziz Abdulla Dept. of Computer Systems P.O. Box 325 S751 05 Uppsala, Sweden parosh@docs.uu.se Karlis Cerans Institute of Mathematics and Computer Science University of Latvia karlis@cclu.lv Abstract We prove that the simulation preorder is decidable for the class of onecounter nets. A onecounter net consists of a finitestate machine operating on a variable (counter) which ranges over the natural numbers. Each transition can increase or decrease the value of the counter. A transition may not be performed if this implies that the value of the counter becomes negative. The class of onecounter nets is computationally equivalent to the class of Petri nets with one unbounded place, and to the class of pushdown automata where the stack alphabet is restricted to one symbol. To our knowledge, this is the first result in the literature which gives a positive answer to the decidability of simulation preorder between pairs of processes in a class whose elements are neither finit...
Designs of Bisimilar Petri Net Controllers with Fault Tolerance Capabilities
"... AbstractThis paper proposes an approach for providing tolerance against faults that may compromise the functionality of a given controller that is modeled by a Petri net. The method is based on embedding the given Petri net controller into a larger (redundant) Petri net controller that retains the ..."
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AbstractThis paper proposes an approach for providing tolerance against faults that may compromise the functionality of a given controller that is modeled by a Petri net. The method is based on embedding the given Petri net controller into a larger (redundant) Petri net controller that retains the original functionality and properties, and uses additional places, connections and tokens to impose invariant conditions that allow the systematic detection and identification of faults via linear parity checks. In particular, the paper considers two types of redundant Petri net controllers: (i) nonseparate redundant Petri net controllers have the same functionality as the given Petri net controller and allow for fault detection and identification, but do not necessarily retain the given controller intact, and; (ii) separate redundant Petri net controllers are a special case of the nonseparate redundant controllers that retain the given Petri net controller intact but enhance it with additional places to enable fault detection and identification. The work in the paper obtains complete characterizations of both types of redundant controllers along with necessary and sufficient conditions for them to be bisimulation equivalent to the given, original Petri net controller. In addition, the paper discusses how each type of redundant controllers can be designed to have desirable fault detection and identification capabilities. When the bisimulation equivalence requirement is not directly enforced, nonseparate redundant controllers can potentially have advantages over separate ones (e.g., they can use fewer connections to detect and identify the same number of faults). An example of a Petri net controller for a production cell and its fault tolerance capabilities using separate and nonseparate embeddings are used to illustrate the approach.
Notes: Joint work with:
, 2004
"... Recently, opacity has proved to be a very promising technique for describing security properties. Much of the work has been couched in terms of Petri nets. Here, we extend the notion of opacity to the model of labelled transition systems and generalize opacity in order to be able to represent inform ..."
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Recently, opacity has proved to be a very promising technique for describing security properties. Much of the work has been couched in terms of Petri nets. Here, we extend the notion of opacity to the model of labelled transition systems and generalize opacity in order to be able to represent information flow security as well as protocol security. We give precise links between opacity and other information flow security definitions such as anonymity or noninterference and between opacity and formal methods applied to protocols in the case of a bounded number of sessions. We also detail a safe way to approximate initial opacity in the case of Petri nets that allows efficient checking of opacity. We illustrate this by two examples, one describing anonymity in a commercial context and the other modelling requirements upon a simple vote system.
Newcastle upon Tyne, NE1 7RU, UK. Opacity Generalised to Transition Systems
, 2004
"... Abstract. Recently, opacity has proved to be a promising technique for describing security properties. Much of the work has been couched in terms of Petri nets. Here, we extend the notion of opacity to the model of labelled transition systems and generalise opacity in order to better represent conce ..."
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Abstract. Recently, opacity has proved to be a promising technique for describing security properties. Much of the work has been couched in terms of Petri nets. Here, we extend the notion of opacity to the model of labelled transition systems and generalise opacity in order to better represent concepts from the work on information flow. In particular, we establish links between opacity and the information flow concepts of anonymity and noninterference such as noninference. We also investigate ways of verifying opacity when working with Petri nets. Our work is illustrated by two examples, one describing anonymity in a commercial context, and the other modelling requirements upon a simple voting system.