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Documents authored by Barozzini, David

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Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2022.112
Unboundedness for Recursion Schemes: A Simpler Type System

Authors: David Barozzini, Paweł Parys, and Jan Wróblewski

Published in: LIPIcs, Volume 229, 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)

Abstract
Decidability of the problems of unboundedness and simultaneous unboundedness (aka. the diagonal problem) for higher-order recursion schemes was established by Clemente, Parys, Salvati, and Walukiewicz (2016). Then a procedure of optimal complexity was presented by Parys (2017); this procedure used a complicated type system, involving multiple flags and markers. We present here a simpler and much more intuitive type system serving the same purpose. We prove that this type system allows to solve the unboundedness problem for a widely considered subclass of recursion schemes, called safe schemes. For unsafe recursion schemes we only have soundness of the type system: if one can establish a type derivation claiming that a recursion scheme is unbounded then it is indeed unbounded. Completeness of the type system for unsafe recursion schemes is left as an open question. Going further, we discuss an extension of the type system that allows to handle the simultaneous unboundedness problem. We also design and implement an algorithm that fully automatically checks unboundedness of a given recursion scheme, completing in a short time for a wide variety of inputs.
Cite as

David Barozzini, Paweł Parys, and Jan Wróblewski. Unboundedness for Recursion Schemes: A Simpler Type System. In 49th International Colloquium on Automata, Languages, and Programming (ICALP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 229, pp. 112:1-112:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{barozzini_et_al:LIPIcs.ICALP.2022.112,
  author =	{Barozzini, David and Parys, Pawe{\l} and Wr\'{o}blewski, Jan},
  title =	{{Unboundedness for Recursion Schemes: A Simpler Type System}},
  booktitle =	{49th International Colloquium on Automata, Languages, and Programming (ICALP 2022)},
  pages =	{112:1--112:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-235-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{229},
  editor =	{Boja\'{n}czyk, Miko{\l}aj and Merelli, Emanuela and Woodruff, David P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2022.112},
  URN =		{urn:nbn:de:0030-drops-164533},
  doi =		{10.4230/LIPIcs.ICALP.2022.112},
  annote =	{Keywords: Higher-order recursion schemes, boundedness, intersection types, safe schemes}
}
Document
Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2020.109
Cost Automata, Safe Schemes, and Downward Closures

Authors: David Barozzini, Lorenzo Clemente, Thomas Colcombet, and Paweł Parys

Published in: LIPIcs, Volume 168, 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)

Abstract
Higher-order recursion schemes are an expressive formalism used to define languages of possibly infinite ranked trees. They extend regular and context-free grammars, and are equivalent to simply typed λY-calculus and collapsible pushdown automata. In this work we prove, under a syntactical constraint called safety, decidability of the model-checking problem for recursion schemes against properties defined by alternating B-automata, an extension of alternating parity automata for infinite trees with a boundedness acceptance condition. We then exploit this result to show how to compute downward closures of languages of finite trees recognized by safe recursion schemes.
Cite as

David Barozzini, Lorenzo Clemente, Thomas Colcombet, and Paweł Parys. Cost Automata, Safe Schemes, and Downward Closures. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 109:1-109:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{barozzini_et_al:LIPIcs.ICALP.2020.109,
  author =	{Barozzini, David and Clemente, Lorenzo and Colcombet, Thomas and Parys, Pawe{\l}},
  title =	{{Cost Automata, Safe Schemes, and Downward Closures}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{109:1--109:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.109},
  URN =		{urn:nbn:de:0030-drops-125169},
  doi =		{10.4230/LIPIcs.ICALP.2020.109},
  annote =	{Keywords: Cost logics, cost automata, downward closures, higher-order recursion schemes, safe recursion schemes}
}
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