14 Search Results for "Meyer, Thomas"

Document
DOI: 10.4230/LIPIcs.SEA.2023.3
Partitioning the Bags of a Tree Decomposition into Cliques

Authors: Thomas Bläsius, Maximilian Katzmann, and Marcus Wilhelm

Published in: LIPIcs, Volume 265, 21st International Symposium on Experimental Algorithms (SEA 2023)

Abstract
We consider a variant of treewidth that we call clique-partitioned treewidth in which each bag is partitioned into cliques. This is motivated by the recent development of FPT-algorithms based on similar parameters for various problems. With this paper, we take a first step towards computing clique-partitioned tree decompositions. Our focus lies on the subproblem of computing clique partitions, i.e., for each bag of a given tree decomposition, we compute an optimal partition of the induced subgraph into cliques. The goal here is to minimize the product of the clique sizes (plus 1). We show that this problem is NP-hard. We also describe four heuristic approaches as well as an exact branch-and-bound algorithm. Our evaluation shows that the branch-and-bound solver is sufficiently efficient to serve as a good baseline. Moreover, our heuristics yield solutions close to the optimum. As a bonus, our algorithms allow us to compute first upper bounds for the clique-partitioned treewidth of real-world networks. A comparison to traditional treewidth indicates that clique-partitioned treewidth is a promising parameter for graphs with high clustering.
Cite as

Thomas Bläsius, Maximilian Katzmann, and Marcus Wilhelm. Partitioning the Bags of a Tree Decomposition into Cliques. In 21st International Symposium on Experimental Algorithms (SEA 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 265, pp. 3:1-3:19, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)

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@InProceedings{blasius_et_al:LIPIcs.SEA.2023.3,
  author =	{Bl\"{a}sius, Thomas and Katzmann, Maximilian and Wilhelm, Marcus},
  title =	{{Partitioning the Bags of a Tree Decomposition into Cliques}},
  booktitle =	{21st International Symposium on Experimental Algorithms (SEA 2023)},
  pages =	{3:1--3:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-279-2},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{265},
  editor =	{Georgiadis, Loukas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2023.3},
  URN =		{urn:nbn:de:0030-drops-183533},
  doi =		{10.4230/LIPIcs.SEA.2023.3},
  annote =	{Keywords: treewidth, weighted treewidth, algorithm engineering, cliques, clustering, complex networks}
}
Document
DOI: 10.4230/LIPIcs.SEA.2023.5
Engineering Shared-Memory Parallel Shuffling to Generate Random Permutations In-Place

Authors: Manuel Penschuck

Published in: LIPIcs, Volume 265, 21st International Symposium on Experimental Algorithms (SEA 2023)

Abstract
Shuffling is the process of placing elements into a random order such that any permutation occurs with equal probability. It is an important building block in virtually all scientific areas. We engineer, - to the best of our knowledge - for the first time, a practically fast, parallel shuffling algorithm with O(√n log n) parallel depth that requires only poly-logarithmic auxiliary memory (with high probability). In an empirical evaluation, we compare our implementations with a number of existing solutions on various computer architectures. Our algorithms consistently achieve the highest through-put on all machines. Further, we demonstrate that the runtime of our parallel algorithm is comparable to the time that other algorithms may take to acquire the memory from the operating system to copy the input.
Cite as

Manuel Penschuck. Engineering Shared-Memory Parallel Shuffling to Generate Random Permutations In-Place. In 21st International Symposium on Experimental Algorithms (SEA 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 265, pp. 5:1-5:20, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)

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@InProceedings{penschuck:LIPIcs.SEA.2023.5,
  author =	{Penschuck, Manuel},
  title =	{{Engineering Shared-Memory Parallel Shuffling to Generate Random Permutations In-Place}},
  booktitle =	{21st International Symposium on Experimental Algorithms (SEA 2023)},
  pages =	{5:1--5:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-279-2},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{265},
  editor =	{Georgiadis, Loukas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2023.5},
  URN =		{urn:nbn:de:0030-drops-183550},
  doi =		{10.4230/LIPIcs.SEA.2023.5},
  annote =	{Keywords: Shuffling, random permutation, parallelism, in-place, algorithm engineering, practical implementation}
}
Document
DOI: 10.4230/LIPIcs.SEA.2023.8
Noisy Sorting Without Searching: Data Oblivious Sorting with Comparison Errors

Authors: Ramtin Afshar, Michael Dillencourt, Michael T. Goodrich, and Evrim Ozel

Published in: LIPIcs, Volume 265, 21st International Symposium on Experimental Algorithms (SEA 2023)

Abstract
We provide and study several algorithms for sorting an array of n comparable distinct elements subject to probabilistic comparison errors. In this model, the comparison of two elements returns the wrong answer according to a fixed probability, p_e < 1/2, and otherwise returns the correct answer. The dislocation of an element is the distance between its position in a given (current or output) array and its position in a sorted array. There are various algorithms that can be utilized for sorting or near-sorting elements subject to probabilistic comparison errors, but these algorithms are not data oblivious because they all make heavy use of noisy binary searching. In this paper, we provide new methods for sorting with comparison errors that are data oblivious while avoiding the use of noisy binary search methods. In addition, we experimentally compare our algorithms and other sorting algorithms.
Cite as

Ramtin Afshar, Michael Dillencourt, Michael T. Goodrich, and Evrim Ozel. Noisy Sorting Without Searching: Data Oblivious Sorting with Comparison Errors. In 21st International Symposium on Experimental Algorithms (SEA 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 265, pp. 8:1-8:18, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)

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@InProceedings{afshar_et_al:LIPIcs.SEA.2023.8,
  author =	{Afshar, Ramtin and Dillencourt, Michael and Goodrich, Michael T. and Ozel, Evrim},
  title =	{{Noisy Sorting Without Searching: Data Oblivious Sorting with Comparison Errors}},
  booktitle =	{21st International Symposium on Experimental Algorithms (SEA 2023)},
  pages =	{8:1--8:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-279-2},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{265},
  editor =	{Georgiadis, Loukas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2023.8},
  URN =		{urn:nbn:de:0030-drops-183585},
  doi =		{10.4230/LIPIcs.SEA.2023.8},
  annote =	{Keywords: sorting, algorithms, randomization, experimentation}
}
Document
DOI: 10.4230/DagRep.12.7.62
Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Seminar 22282)

Authors: James P. Delgrande, Birte Glimm, Thomas Meyer, Miroslaw Truszczynski, Milene Santos Teixeira, and Frank Wolter

Published in: Dagstuhl Reports, Volume 12, Issue 7 (2023)

Abstract
The area of Knowledge Representation and Reasoning (KR) is a central area in Artificial Intelligence that deals with the explicit, declarative representation of knowledge along with inference procedures for deriving further, implicit information from this knowledge. The goal of this Perspectives Seminar was to assess the area of KR, including its history, current state, and future prospects, and from this assessment to provide suggestions and recommendations for advancing the field, increasing participation in the area, and furthering links with related areas. Over the course of 5 days, 25 participants from a cross-section of subareas in KR and areas adjacent to KR met to discuss these topics. The workshop was composed of a number of invited talks and panels for reviewing the history and state of the art of KR, along with several working groups and general open discussions. In common with other Perspectives Workshops, a Manifesto will be produced; as well, recommendations contained in the manifesto will be also forwarded to the steering committee of the Principles of Knowledge Representation and Reasoning conference series for their consideration.
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James P. Delgrande, Birte Glimm, Thomas Meyer, Miroslaw Truszczynski, Milene Santos Teixeira, and Frank Wolter. Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Seminar 22282). In Dagstuhl Reports, Volume 12, Issue 7, pp. 62-79, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)

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@Article{delgrande_et_al:DagRep.12.7.62,
  author =	{Delgrande, James P. and Glimm, Birte and Meyer, Thomas and Truszczynski, Miroslaw and Teixeira, Milene Santos and Wolter, Frank},
  title =	{{Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Seminar 22282)}},
  pages =	{62--79},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2023},
  volume =	{12},
  number =	{7},
  editor =	{Delgrande, James P. and Glimm, Birte and Meyer, Thomas and Truszczynski, Miroslaw and Teixeira, Milene Santos and Wolter, Frank},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.12.7.62},
  URN =		{urn:nbn:de:0030-drops-176126},
  doi =		{10.4230/DagRep.12.7.62},
  annote =	{Keywords: applications of logics, declarative representations, formal logic, knowledge representation and reasoning}
}
Document
DOI: 10.4230/LITES.8.2.2
Swarms of Mobile Robots: Towards Versatility with Safety

Authors: Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain

Published in: LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2

Abstract
We present Pactole, a formal framework to design and prove the correctness of protocols (or the impossibility of their existence) that target mobile robotic swarms. Unlike previous approaches, our methodology unifies in a single formalism the execution model, the problem specification, the protocol, and its proof of correctness. The Pactole framework makes use of the Coq proof assistant, and is specially targeted at protocol designers and problem specifiers, so that a common unambiguous language is used from the very early stages of protocol development. We stress the underlying framework design principles to enable high expressivity and modularity, and provide concrete examples about how the Pactole framework can be used to tackle actual problems, some previously addressed by the Distributed Computing community, but also new problems, while being certified correct.
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Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain. Swarms of Mobile Robots: Towards Versatility with Safety. In LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2, pp. 02:1-02:36, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@Article{courtieu_et_al:LITES.8.2.2,
  author =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  title =	{{Swarms of Mobile Robots: Towards Versatility with Safety}},
  booktitle =	{LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems},
  pages =	{02:1--02:36},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2022},
  volume =	{8},
  number =	{2},
  editor =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.8.2.2},
  doi =		{10.4230/LITES.8.2.2},
  annote =	{Keywords: distributed algorithm, mobile autonomous robots, formal proof}
}
Document
DOI: 10.4230/LITES.7.1.2
We know what you're doing! Application detection using thermal data

Authors: Philipp Miedl, Rehan Ahmed, and Lothar Thiele

Published in: LITES, Volume 7, Issue 1 (2021): Special Issue on Embedded System Security. Leibniz Transactions on Embedded Systems, Volume 7, Issue 1

Abstract
Modern mobile and embedded devices have high computing power which allows them to be used for multiple purposes. Therefore, applications with low security restrictions may execute on the same device as applications handling highly sensitive information. In such a setup, a security risk occurs if it is possible that an application uses system characteristics to gather information about another application on the same device.In this work, we present a method to leak sensitive runtime information by just using temperature sensor readings of a mobile device. We employ a Convolutional-Neural-Network, Long Short-Term Memory units and subsequent label sequence processing to identify the sequence of executed applications over time. To test our hypothesis we collect data from two state-of-the-art smartphones and real user usage patterns. We show an extensive evaluation using laboratory data, where we achieve labelling accuracies up to 90% and negligible timing error. Based on our analysis we state that the thermal information can be used to compromise sensitive user data and increase the vulnerability of mobile devices. A study based on data collected outside of the laboratory opens up various future directions for research.
Cite as

Philipp Miedl, Rehan Ahmed, and Lothar Thiele. We know what you're doing! Application detection using thermal data. In LITES, Volume 7, Issue 1 (2021): Special Issue on Embedded System Security. Leibniz Transactions on Embedded Systems, Volume 7, Issue 1, pp. 02:1-02:28, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2021)

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@Article{miedl_et_al:LITES.7.1.2,
  author =	{Miedl, Philipp and Ahmed, Rehan and Thiele, Lothar},
  title =	{{We know what you're doing! Application detection using thermal data}},
  booktitle =	{LITES, Volume 7, Issue 1 (2021): Special Issue on Embedded System Security},
  pages =	{02:1--02:28},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2021},
  volume =	{7},
  number =	{1},
  editor =	{Miedl, Philipp and Ahmed, Rehan and Thiele, Lothar},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.7.1.2},
  doi =		{10.4230/LITES.7.1.2},
  annote =	{Keywords: Thermal Monitoring, Side Channel, Data Leak, Sequence Labelling}
}
Document
Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2021.123
Optimal Transformations of Games and Automata Using Muller Conditions

Authors: Antonio Casares, Thomas Colcombet, and Nathanaël Fijalkow

Published in: LIPIcs, Volume 198, 48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)

Abstract
We consider the following question: given an automaton or a game with a Muller condition, how can we efficiently construct an equivalent one with a parity condition? There are several examples of such transformations in the literature, including in the determinisation of Büchi automata. We define a new transformation called the alternating cycle decomposition, inspired and extending Zielonka’s construction. Our transformation operates on transition systems, encompassing both automata and games, and preserves semantic properties through the existence of a locally bijective morphism. We show a strong optimality result: the obtained parity transition system is minimal both in number of states and number of priorities with respect to locally bijective morphisms. We give two applications: the first is related to the determinisation of Büchi automata, and the second is to give crisp characterisations on the possibility of relabelling automata with different acceptance conditions.
Cite as

Antonio Casares, Thomas Colcombet, and Nathanaël Fijalkow. Optimal Transformations of Games and Automata Using Muller Conditions. In 48th International Colloquium on Automata, Languages, and Programming (ICALP 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 198, pp. 123:1-123:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2021)

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@InProceedings{casares_et_al:LIPIcs.ICALP.2021.123,
  author =	{Casares, Antonio and Colcombet, Thomas and Fijalkow, Nathana\"{e}l},
  title =	{{Optimal Transformations of Games and Automata Using Muller Conditions}},
  booktitle =	{48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)},
  pages =	{123:1--123:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-195-5},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{198},
  editor =	{Bansal, Nikhil and Merelli, Emanuela and Worrell, James},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2021.123},
  URN =		{urn:nbn:de:0030-drops-141928},
  doi =		{10.4230/LIPIcs.ICALP.2021.123},
  annote =	{Keywords: Automata over infinite words, Omega regular languages, Determinisation of automata}
}
Document
DOI: 10.4230/LIPIcs.ESA.2019.21
Efficiently Generating Geometric Inhomogeneous and Hyperbolic Random Graphs

Authors: Thomas Bläsius, Tobias Friedrich, Maximilian Katzmann, Ulrich Meyer, Manuel Penschuck, and Christopher Weyand

Published in: LIPIcs, Volume 144, 27th Annual European Symposium on Algorithms (ESA 2019)

Abstract
Hyperbolic random graphs (HRG) and geometric inhomogeneous random graphs (GIRG) are two similar generative network models that were designed to resemble complex real world networks. In particular, they have a power-law degree distribution with controllable exponent beta, and high clustering that can be controlled via the temperature T. We present the first implementation of an efficient GIRG generator running in expected linear time. Besides varying temperatures, it also supports underlying geometries of higher dimensions. It is capable of generating graphs with ten million edges in under a second on commodity hardware. The algorithm can be adapted to HRGs. Our resulting implementation is the fastest sequential HRG generator, despite the fact that we support non-zero temperatures. Though non-zero temperatures are crucial for many applications, most existing generators are restricted to T = 0. We also support parallelization, although this is not the focus of this paper. Moreover, we note that our generators draw from the correct probability distribution, i.e., they involve no approximation. Besides the generators themselves, we also provide an efficient algorithm to determine the non-trivial dependency between the average degree of the resulting graph and the input parameters of the GIRG model. This makes it possible to specify the desired expected average degree as input. Moreover, we investigate the differences between HRGs and GIRGs, shedding new light on the nature of the relation between the two models. Although HRGs represent, in a certain sense, a special case of the GIRG model, we find that a straight-forward inclusion does not hold in practice. However, the difference is negligible for most use cases.
Cite as

Thomas Bläsius, Tobias Friedrich, Maximilian Katzmann, Ulrich Meyer, Manuel Penschuck, and Christopher Weyand. Efficiently Generating Geometric Inhomogeneous and Hyperbolic Random Graphs. In 27th Annual European Symposium on Algorithms (ESA 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 144, pp. 21:1-21:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{blasius_et_al:LIPIcs.ESA.2019.21,
  author =	{Bl\"{a}sius, Thomas and Friedrich, Tobias and Katzmann, Maximilian and Meyer, Ulrich and Penschuck, Manuel and Weyand, Christopher},
  title =	{{Efficiently Generating Geometric Inhomogeneous and Hyperbolic Random Graphs}},
  booktitle =	{27th Annual European Symposium on Algorithms (ESA 2019)},
  pages =	{21:1--21:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-124-5},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{144},
  editor =	{Bender, Michael A. and Svensson, Ola and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2019.21},
  URN =		{urn:nbn:de:0030-drops-111424},
  doi =		{10.4230/LIPIcs.ESA.2019.21},
  annote =	{Keywords: hyperbolic random graphs, geometric inhomogeneous random graph, efficient network generation}
}
Document
DOI: 10.4230/DagRep.9.2.73
The Role of Non-monotonic Reasoning in Future Development of Artificial Intelligence (Dagstuhl Perspectives Workshop 19072)

Authors: Anthony Hunter, Gabriele Kern-Isberner, Thomas Meyer, and Renata Wassermann

Published in: Dagstuhl Reports, Volume 9, Issue 2 (2019)

Abstract
This report documents the program and the outcomes of Dagstuhl Perspectives Workshop 19072 "The Role of Non-monotonic Reasoning in Future Development of Artificial Intelligence". The workshop brought together researchers both from core topics and peripheral areas of non-monotonic reasoning (NMR), but also attracted researchers from other scientific domains in which recent developments have shown an increased relevance of NMR topics. The overall goal of this workshop was to reshape NMR as a core methodology for artificial intelligence being able to meet present and future challenges. Participants of this workshop discussed in what shape NMR would be useful for future AI, and how NMR can be developed for those requirements. The workshop started with brief survey talks and had some technical talks on central topics of NMR afterwards. These were followed by working groups on core aspects of NMR and potential links with learning. On the last day of the seminar, each working group presented their ideas and future plans. The workshop closed with a plenary discussion on the future of NMR.
Cite as

Anthony Hunter, Gabriele Kern-Isberner, Thomas Meyer, and Renata Wassermann. The Role of Non-monotonic Reasoning in Future Development of Artificial Intelligence (Dagstuhl Perspectives Workshop 19072). In Dagstuhl Reports, Volume 9, Issue 2, pp. 73-90, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@Article{hunter_et_al:DagRep.9.2.73,
  author =	{Hunter, Anthony and Kern-Isberner, Gabriele and Meyer, Thomas and Wassermann, Renata},
  title =	{{The Role of Non-monotonic Reasoning in Future Development of Artificial Intelligence (Dagstuhl Perspectives Workshop 19072)}},
  pages =	{73--90},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2019},
  volume =	{9},
  number =	{2},
  editor =	{Hunter, Anthony and Kern-Isberner, Gabriele and Meyer, Thomas and Wassermann, Renata},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.9.2.73},
  URN =		{urn:nbn:de:0030-drops-108601},
  doi =		{10.4230/DagRep.9.2.73},
  annote =	{Keywords: Artificial intelligence, Knowledge representation and reasoning, Nonmonotonic, default reasoning and belief revision, Probabilistic reasoning, Logic programming and answer set programming, Ontology engineering, Cognitive science, Machine learning}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2017.5
Bidirectional Nested Weighted Automata

Authors: Krishnendu Chatterjee, Thomas A. Henzinger, and Jan Otop

Published in: LIPIcs, Volume 85, 28th International Conference on Concurrency Theory (CONCUR 2017)

Abstract
Nested weighted automata (NWA) present a robust and convenient automata-theoretic formalism for quantitative specifications. Previous works have considered NWA that processed input words only in the forward direction. It is natural to allow the automata to process input words backwards as well, for example, to measure the maximal or average time between a response and the preceding request. We therefore introduce and study bidirectional NWA that can process input words in both directions. First, we show that bidirectional NWA can express interesting quantitative properties that are not expressible by forward-only NWA. Second, for the fundamental decision problems of emptiness and universality, we establish decidability and complexity results for the new framework which match the best-known results for the special case of forward-only NWA. Thus, for NWA, the increased expressiveness of bidirectionality is achieved at no additional computational complexity. This is in stark contrast to the unweighted case, where bidirectional finite automata are no more expressive but exponentially more succinct than their forward-only counterparts.
Cite as

Krishnendu Chatterjee, Thomas A. Henzinger, and Jan Otop. Bidirectional Nested Weighted Automata. In 28th International Conference on Concurrency Theory (CONCUR 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 85, pp. 5:1-5:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)

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@InProceedings{chatterjee_et_al:LIPIcs.CONCUR.2017.5,
  author =	{Chatterjee, Krishnendu and Henzinger, Thomas A. and Otop, Jan},
  title =	{{Bidirectional Nested Weighted Automata}},
  booktitle =	{28th International Conference on Concurrency Theory (CONCUR 2017)},
  pages =	{5:1--5:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-048-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{85},
  editor =	{Meyer, Roland and Nestmann, Uwe},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2017.5},
  URN =		{urn:nbn:de:0030-drops-77763},
  doi =		{10.4230/LIPIcs.CONCUR.2017.5},
  annote =	{Keywords: weighted automata, nested weighted automata, complexity, bidirectional}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2017.18
Goal-Driven Unfolding of Petri Nets

Authors: Thomas Chatain and Loïc Paulevé

Published in: LIPIcs, Volume 85, 28th International Conference on Concurrency Theory (CONCUR 2017)

Abstract
Unfoldings provide an efficient way to avoid the state-space explosion due to interleavings of concurrent transitions when exploring the runs of a Petri net. The theory of adequate orders allows one to define finite prefixes of unfoldings which contain all the reachable markings. In this paper we are interested in reachability of a single given marking, called the goal. We propose an algorithm for computing a finite prefix of the unfolding of a 1-safe Petri net that preserves all minimal configurations reaching this goal. Our algorithm combines the unfolding technique with on-the-fly model reduction by static analysis aiming at avoiding the exploration of branches which are not needed for reaching the goal. We present some experimental results.
Cite as

Thomas Chatain and Loïc Paulevé. Goal-Driven Unfolding of Petri Nets. In 28th International Conference on Concurrency Theory (CONCUR 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 85, pp. 18:1-18:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)

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@InProceedings{chatain_et_al:LIPIcs.CONCUR.2017.18,
  author =	{Chatain, Thomas and Paulev\'{e}, Lo\"{i}c},
  title =	{{Goal-Driven Unfolding of Petri Nets}},
  booktitle =	{28th International Conference on Concurrency Theory (CONCUR 2017)},
  pages =	{18:1--18:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-048-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{85},
  editor =	{Meyer, Roland and Nestmann, Uwe},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2017.18},
  URN =		{urn:nbn:de:0030-drops-77730},
  doi =		{10.4230/LIPIcs.CONCUR.2017.18},
  annote =	{Keywords: model reduction; reachability; concurrency; unfoldings; Petri nets; automata networks}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2017.21
Infinite-Duration Bidding Games

Authors: Guy Avni, Thomas A. Henzinger, and Ventsislav Chonev

Published in: LIPIcs, Volume 85, 28th International Conference on Concurrency Theory (CONCUR 2017)

Abstract
Two-player games on graphs are widely studied in formal methods as they model the interaction between a system and its environment. The game is played by moving a token throughout a graph to produce an infinite path. There are several common modes to determine how the players move the token through the graph; e.g., in turn-based games the players alternate turns in moving the token. We study the bidding mode of moving the token, which, to the best of our knowledge, has never been studied in infinite-duration games. Both players have separate budgets, which sum up to $1$. In each turn, a bidding takes place. Both players submit bids simultaneously, and a bid is legal if it does not exceed the available budget. The winner of the bidding pays his bid to the other player and moves the token. For reachability objectives, repeated bidding games have been studied and are called Richman games [Lazarus1999,Lazarus2012]. There, a central question is the existence and computation of threshold budgets; namely, a value t \in [0,1] such that if \PO's budget exceeds t, he can win the game, and if \PT's budget exceeds 1-t, he can win the game. We focus on parity games and mean-payoff games. We show the existence of threshold budgets in these games, and reduce the problem of finding them to Richman games. We also determine the strategy-complexity of an optimal strategy. Our most interesting result shows that memoryless strategies suffice for mean-payoff bidding games.
Cite as

Guy Avni, Thomas A. Henzinger, and Ventsislav Chonev. Infinite-Duration Bidding Games. In 28th International Conference on Concurrency Theory (CONCUR 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 85, pp. 21:1-21:18, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2017)

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@InProceedings{avni_et_al:LIPIcs.CONCUR.2017.21,
  author =	{Avni, Guy and Henzinger, Thomas A. and Chonev, Ventsislav},
  title =	{{Infinite-Duration Bidding Games}},
  booktitle =	{28th International Conference on Concurrency Theory (CONCUR 2017)},
  pages =	{21:1--21:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-048-4},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{85},
  editor =	{Meyer, Roland and Nestmann, Uwe},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2017.21},
  URN =		{urn:nbn:de:0030-drops-77741},
  doi =		{10.4230/LIPIcs.CONCUR.2017.21},
  annote =	{Keywords: Bidding Games, Parity Games, Mean-Payoff Games, Richman Games}
}
Document
DOI: 10.4230/DagRep.2.10.105
Foundations and Challenges of Change and Evolution in Ontologies (Dagstuhl Seminar 12441)

Authors: James Delgrande, Thomas Meyer, and Ulrike Sattler

Published in: Dagstuhl Reports, Volume 2, Issue 10 (2013)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 12441 "Foundations and Challenges of Change and Evolution in Ontologies", held from 28 October to 2 November 2012. The aim of the workshop was to bring together researchers working in the areas of logic-based ontologies, belief change, and database systems, along with researchers working in relevant areas in nonmonotonic reasoning, commonsense reasoning, and paraconsistent reasoning. The workshop provided a forum for discussions on the application of existing work in belief change, nonmonotonic reasoning, commonsense reasoning, and databases to logic-based ontologies. Overall the intent was to provide an interdisciplinary (with respect to computer science and mathematics) workshop for addressing both theoretical and computational issues in managing change and evolution in formal ontologies.
Cite as

James Delgrande, Thomas Meyer, and Ulrike Sattler. Foundations and Challenges of Change and Evolution in Ontologies (Dagstuhl Seminar 12441). In Dagstuhl Reports, Volume 2, Issue 10, pp. 105-116, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2013)

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@Article{delgrande_et_al:DagRep.2.10.105,
  author =	{Delgrande, James and Meyer, Thomas and Sattler, Ulrike},
  title =	{{Foundations and Challenges of Change and Evolution in Ontologies (Dagstuhl Seminar 12441)}},
  pages =	{105--116},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2013},
  volume =	{2},
  number =	{10},
  editor =	{Delgrande, James and Meyer, Thomas and Sattler, Ulrike},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.2.10.105},
  URN =		{urn:nbn:de:0030-drops-39079},
  doi =		{10.4230/DagRep.2.10.105},
  annote =	{Keywords: Artificial intelligence, Belief change, Ontologies, Description logics}
}
Document
DOI: 10.4230/DFU.SciViz.2010.227
From Visualization to Visually Enabled Reasoning

Authors: Joerg Meyer, Jim Thomas, Stephan Diehl, Brian Fisher, and Daniel A. Keim

Published in: Dagstuhl Follow-Ups, Volume 1, Scientific Visualization: Advanced Concepts (2010)

Abstract
Interactive Visualization has been used to study scientific phenomena, analyze data, visualize information, and to explore large amounts of multi-variate data. It enables the human mind to gain novel insights by empowering the human visual system, encompassing the brain and the eyes, to discover properties that were previously unknown. While it is believed that the process of creating interactive visualizations is reasonably well understood, the process of stimulating and enabling human reasoning with the aid of interactive visualization tools is still a highly unexplored field. We hypothesize that visualizations make an impact if they successfully influence a thought process or a decision. Interacting with visualizations is part of this process. We present exemplary cases where visualization was successful in enabling human reasoning, and instances where the interaction with data helped in understanding the data and making a better informed decision. We suggest metrics that help in understanding the evolution of a decision making process. Such a metric would measure the efficiency of the reasoning process, rather than the performance of the visualization system or the user. We claim that the methodology of interactive visualization, which has been studied to a great extent, is now sufficiently mature, and we would like to provide some guidance regarding the evaluation of knowledge gain through visually enabled reasoning. It is our ambition to encourage the reader to take on the next step and move from information visualization to visually enabled reasoning.
Cite as

Joerg Meyer, Jim Thomas, Stephan Diehl, Brian Fisher, and Daniel A. Keim. From Visualization to Visually Enabled Reasoning. In Scientific Visualization: Advanced Concepts. Dagstuhl Follow-Ups, Volume 1, pp. 227-245, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2010)

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@InCollection{meyer_et_al:DFU.SciViz.2010.227,
  author =	{Meyer, Joerg and Thomas, Jim and Diehl, Stephan and Fisher, Brian and Keim, Daniel A.},
  title =	{{From Visualization to Visually Enabled Reasoning}},
  booktitle =	{Scientific Visualization: Advanced Concepts},
  pages =	{227--245},
  series =	{Dagstuhl Follow-Ups},
  ISBN =	{978-3-939897-19-4},
  ISSN =	{1868-8977},
  year =	{2010},
  volume =	{1},
  editor =	{Hagen, Hans},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DFU.SciViz.2010.227},
  URN =		{urn:nbn:de:0030-drops-27078},
  doi =		{10.4230/DFU.SciViz.2010.227},
  annote =	{Keywords: Interactive Visualization, Reasoning}
}
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