## Abstract

We study three levels in a hierarchy of nondeterminism: A nondeterministic automaton A is determinizable by pruning (DBP) if we can obtain a deterministic automaton equivalent to A by removing some of its transitions. Then, A is good-for-games (GFG) if its nondeterministic choices can be resolved in a way that only depends on the past. Finally, A is semantically deterministic (SD) if different nondeterministic choices in A lead to equivalent states. Some applications of automata in formal methods require deterministic automata, yet in fact can use automata with some level of nondeterminism. For example, DBP automata are useful in the analysis of online algorithms, and GFG automata are useful in synthesis and control. For automata on finite words, the three levels in the hierarchy coincide. We study the hierarchy for Büchi, co-Büchi, and weak automata on infinite words. We show that the hierarchy is strict, study the expressive power of the different levels in it, as well as the complexity of deciding the membership of a language in a given level. Finally, we describe a probability-based analysis of the hierarchy, which relates the level of nondeterminism with the probability that a random run on a word in the language is accepting.

Original language | American English |
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Title of host publication | 46th International Symposium on Mathematical Foundations of Computer Science, MFCS 2021 |

Editors | Filippo Bonchi, Simon J. Puglisi |

Publisher | Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing |

Pages | 85:1-85:21 |

Number of pages | 21 |

ISBN (Electronic) | 9783959772013 |

DOIs | |

State | Published - 1 Aug 2021 |

Event | 46th International Symposium on Mathematical Foundations of Computer Science, MFCS 2021 - Tallinn, Estonia Duration: 23 Aug 2021 → 27 Aug 2021 |

### Publication series

Name | Leibniz International Proceedings in Informatics, LIPIcs |
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Volume | 202 |

ISSN (Print) | 1868-8969 |

### Conference

Conference | 46th International Symposium on Mathematical Foundations of Computer Science, MFCS 2021 |
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Country/Territory | Estonia |

City | Tallinn |

Period | 23/08/21 → 27/08/21 |

### Bibliographical note

Publisher Copyright:© Bader Abu Radi, Orna Kupferman, and Ofer Leshkowitz; licensed under Creative Commons License CC-BY 4.0 46th International Symposium on Mathematical Foundations of Computer Science (MFCS 2021).

## Keywords

- Automata on infinite words
- Complexity
- Expressive power
- Games