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10 results on '"Stüber, Torsten"'

1. Mathematical Analysis and Algorithms for Federated Byzantine Agreement Systems

Author

Gaul, André, Khoffi, Ismail, Liesen, Jörg, and Stüber, Torsten

Subjects
Computer Science - Distributed, Parallel, and Cluster Computing, C.2.4
Abstract

We give an introduction to federated Byzantine agreement systems (FBAS) with many examples ranging from small "academic" cases to the current Stellar network. We then analyze the main concepts from a mathematical and an algorithmic point of view. Based on work of Lachowski we derive algorithms for quorum enumeration, checking quorum intersection, and computing the intact nodes with respect to a given set of ill-behaved (Byzantine) nodes. We also show that from the viewpoint of the intactness probability of nodes, which we introduce in this paper, a hierarchical setup of nodes is inferior to an arrangement that we call a symmetric simple FBAS. All algorithms described in this paper are implemented in the Python package Stellar Observatory, which is also used in some of the computed examples.

Published
2019

2. Monadic Datalog Tree Transducers

Author

Büchse, Matthias, Stüber, Torsten, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Dediu, Adrian Horia, editor, Ionescu, Armand Mihai, editor, and Martín-Vide, Carlos, editor

Published
2009
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7. Consistency of Probabilistic Context-Free Grammars

Author

Stüber, Torsten

Subjects
Context-free Grammar, Probabilistic Context-Free Grammar, Consistency, Natural Language Processing, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, Computer Science::Computation and Language (Computational Linguistics and Natural Language and Speech Processing), Kontextfreie Grammatik, Probabilistische Kontextfreie Grammatik, Konsistenz, Verarbeitung natürlicher Sprachen, ddc:004, Computer Science::Formal Languages and Automata Theory
Abstract

We present an algorithm for deciding whether an arbitrary proper probabilistic context-free grammar is consistent, i.e., whether the probability that a derivation terminates is one. Our procedure has time complexity $\\\\mathcal O(n^3)$ in the unit-cost model of computation. Moreover, we develop a novel characterization of consistent probabilistic context-free grammars. A simple corollary of our result is that training methods for probabilistic context-free grammars that are based on maximum-likelihood estimation always yield consistent grammars.

Published
2012

8. Multioperator Weighted Monadic Datalog

Author

Stüber, Torsten, Vogler, Heiko, Fülöp, Zoltán, and Technische Universität Dresden

Subjects
Automatentheorie, Baumautomaten, Baumübersetzer, Logik, Monadic Datalog, ddc:004, Automata Theory, Tree Automata, Tree Transducer, Logic, Monadic Datalog
Abstract

In this thesis we will introduce multioperator weighted monadic datalog (mwmd), a formal model for specifying tree series, tree transformations, and tree languages. This model combines aspects of multioperator weighted tree automata (wmta), weighted monadic datalog (wmd), and monadic datalog tree transducers (mdtt). In order to develop a rich theory we will define multiple versions of semantics for mwmd and compare their expressiveness. We will study normal forms and decidability results of mwmd and show (by employing particular semantic domains) that the theory of mwmd subsumes the theory of both wmd and mdtt. We conclude this thesis by showing that mwmd even contain wmta as a syntactic subclass and present results concerning this subclass.

Published
2010

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