3 Search Results for "Staiger, Ludwig"

Document
DOI: 10.4230/LIPIcs.CALCO.2019.5
Omega-Automata: A Coalgebraic Perspective on Regular omega-Languages

Authors: Vincenzo Ciancia and Yde Venema

Published in: LIPIcs, Volume 139, 8th Conference on Algebra and Coalgebra in Computer Science (CALCO 2019)

Abstract
In this work, we provide a simple coalgebraic characterisation of regular omega-languages based on languages of lassos, and prove a number of related mathematical results, framed into the theory of a new kind of automata called Omega-automata. In earlier work we introduced Omega-automata as two-sorted structures that naturally operate on lassos, pairs of words encoding ultimately periodic streams (infinite words). Here we extend the scope of these Omega-automata by proposing them as a new kind of acceptor for arbitrary streams. We prove that Omega-automata are expressively complete for the regular omega-languages. We show that, due to their coalgebraic nature, Omega-automata share some attractive properties with deterministic automata operating on finite words, properties that other types of stream automata lack. In particular, we provide a simple, coalgebraic definition of bisimilarity between Omega-automata that exactly captures language equivalence and allows for a simple minimization procedure. We also prove a coalgebraic Myhill-Nerode style theorem for lasso languages, and use this result, in combination with a closure property on stream languages called lasso determinacy, to give a characterization of regular omega-languages.
Cite as

Vincenzo Ciancia and Yde Venema. Omega-Automata: A Coalgebraic Perspective on Regular omega-Languages. In 8th Conference on Algebra and Coalgebra in Computer Science (CALCO 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 139, pp. 5:1-5:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)

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@InProceedings{ciancia_et_al:LIPIcs.CALCO.2019.5,
  author =	{Ciancia, Vincenzo and Venema, Yde},
  title =	{{Omega-Automata: A Coalgebraic Perspective on Regular omega-Languages}},
  booktitle =	{8th Conference on Algebra and Coalgebra in Computer Science (CALCO 2019)},
  pages =	{5:1--5:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-120-7},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{139},
  editor =	{Roggenbach, Markus and Sokolova, Ana},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2019.5},
  URN =		{urn:nbn:de:0030-drops-114338},
  doi =		{10.4230/LIPIcs.CALCO.2019.5},
  annote =	{Keywords: omega-automata, regular omega-languages, coalgebra, streams, bisimilarity}
}
Document
DOI: 10.4230/OASIcs.CCA.2009.2269
On Oscillation-free epsilon-random Sequences II

Authors: Jöran Mielke and Ludwig Staiger

Published in: OASIcs, Volume 11, 6th International Conference on Computability and Complexity in Analysis (CCA'09) (2009)

Abstract
It has been shown (see (Staiger, 2008)), that there are strongly \textsc{Martin-L\"of}-$\varepsilon$-random $\omega$-words that behave in terms of complexity like random $\omega$-words. That is, in particular, the \emph{a priori} complexity of these $\varepsilon$-random $\omega$-words is bounded from below and above by linear functions with the same slope $\varepsilon$. In this paper we will study the set of these $\omega$-words in terms of \textsc{Hausdorff} measure and dimension. Additionally we find upper bounds on \emph{a priori} complexity, monotone and simple complexity for a certain class of $\omega$-power languages.
Cite as

Jöran Mielke and Ludwig Staiger. On Oscillation-free epsilon-random Sequences II. In 6th International Conference on Computability and Complexity in Analysis (CCA'09). Open Access Series in Informatics (OASIcs), Volume 11, pp. 173-184, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2009)

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@InProceedings{mielke_et_al:OASIcs.CCA.2009.2269,
  author =	{Mielke, J\"{o}ran and Staiger, Ludwig},
  title =	{{On Oscillation-free epsilon-random Sequences II}},
  booktitle =	{6th International Conference on Computability and Complexity in Analysis (CCA'09)},
  pages =	{173--184},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-12-5},
  ISSN =	{2190-6807},
  year =	{2009},
  volume =	{11},
  editor =	{Bauer, Andrej and Hertling, Peter and Ko, Ker-I},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.CCA.2009.2269},
  URN =		{urn:nbn:de:0030-drops-22698},
  doi =		{10.4230/OASIcs.CCA.2009.2269},
  annote =	{Keywords: Omega-words, partial randomness, a priori complexity, monotone complexity}
}
Document
DOI: 10.4230/DagSemProc.08271.7
Topological Complexity of omega-Powers: Extended Abstract

Authors: Olivier Finkel and Dominique Lecomte

Published in: Dagstuhl Seminar Proceedings, Volume 8271, Topological and Game-Theoretic Aspects of Infinite Computations (2008)

Abstract
The operation of taking the omega-power $V^omega$ of a language $V$ is a fundamental operation over finitary languages leading to omega-languages. Since the set $X^omega$ of infinite words over a finite alphabet $X$ can be equipped with the usual Cantor topology, the question of the topological complexity of omega-powers of finitary languages naturally arises and has been posed by Damian Niwinski (1990), Pierre Simonnet (1992), and Ludwig Staiger (1997). We investigate the topological complexity of omega-powers. We prove the following very surprising results which show that omega-powers exhibit a great opological complexity: for each non-null countable ordinal $xi$, there exist some $Sigma^0_xi$-complete omega-powers, and some $Pi^0_xi$-complete omega-powers. On the other hand, the Wadge hierarchy is a great refinement of the Borel hierarchy, determined by Bill Wadge. We show that, for each ordinal $xi$ greater than or equal to 3, there are uncountably many Wadge degrees of omega-powers of Borel rank $xi +1$. Using tools of effective descriptive set theory, we prove some effective versions of the above results.
Cite as

Olivier Finkel and Dominique Lecomte. Topological Complexity of omega-Powers: Extended Abstract. In Topological and Game-Theoretic Aspects of Infinite Computations. Dagstuhl Seminar Proceedings, Volume 8271, pp. 1-9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2008)

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@InProceedings{finkel_et_al:DagSemProc.08271.7,
  author =	{Finkel, Olivier and Lecomte, Dominique},
  title =	{{Topological Complexity of omega-Powers: Extended Abstract}},
  booktitle =	{Topological and Game-Theoretic Aspects of Infinite Computations},
  pages =	{1--9},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2008},
  volume =	{8271},
  editor =	{Peter Hertling and Victor Selivanov and Wolfgang Thomas and William W. Wadge and Klaus Wagner},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.08271.7},
  URN =		{urn:nbn:de:0030-drops-16505},
  doi =		{10.4230/DagSemProc.08271.7},
  annote =	{Keywords: Infinite words, omega-languages, omega-powers, Cantor topology, topological complexity, Borel sets, Borel ranks, complete sets, Wadge hierarchy, Wadge}
}
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