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Register pushdown automata (RPDA) is an extension of classical pushdown automata to handle data values in a restricted way. RPDA attracts attention as a model of a query language for structured documents with data values. The membership and…

Formal Languages and Automata Theory · Computer Science 2019-10-24 Ryoma Senda , Yoshiaki Takata , Hiroyuki Seki

We introduce good-for-games $\omega$-pushdown automata ($\omega$-GFG-PDA). These are automata whose nondeterminism can be resolved based on the input processed so far. Good-for-gameness enables automata to be composed with games, trees, and…

Formal Languages and Automata Theory · Computer Science 2023-06-22 Karoliina Lehtinen , Martin Zimmermann

We give a new proof of the decidability of reachability in alternating pushdown systems, showing that it is a simple consequence of a cut-elimination theorem for some natural-deduction style inference systems. Then, we show how this result…

Logic in Computer Science · Computer Science 2014-10-31 Gilles Dowek , Ying Jiang

A complete deterministic finite automaton in which every non-empty subset of the state set occurs as the image of the whole state set under the action of a suitable input word is called completely reachable. We characterize completely…

Formal Languages and Automata Theory · Computer Science 2018-05-09 Eugenija Bondar , Mikhail Volkov

We present a new partial order reduction method for reachability analysis of nondeterministic labeled transition systems over metric spaces. Nondeterminism arises from both the choice of the initial state and the choice of actions, and the…

Logic in Computer Science · Computer Science 2018-05-14 Chuchu Fan , Zhenqi Huang , Sayan Mitra

A turn in a computation of a pushdown automaton is a switch from a phase in which the height of the pushdown store increases to a phase in which it decreases. Given a pushdown or one-counter automaton, we consider, for each string in its…

Formal Languages and Automata Theory · Computer Science 2026-03-10 Giovanni Pighizzini

Reward machines (RMs) are automata structures that encode (non-Markovian) reward functions for reinforcement learning (RL). RMs can reward any behaviour representable in regular languages and, when paired with RL algorithms that exploit RM…

Artificial Intelligence · Computer Science 2025-11-13 Giovanni Varricchione , Toryn Q. Klassen , Natasha Alechina , Mehdi Dastani , Brian Logan , Sheila A. McIlraith

History-deterministic automata are a restricted class of nondeterministic automata where the nondeterminism while reading an input can be resolved successfully based on the prefix read so far. History-deterministic automata are…

Formal Languages and Automata Theory · Computer Science 2026-05-28 Keya Prakash

The question if a deterministic finite automaton admits a software reset in the form of a so-called synchronizing word can be answered in polynomial time. In this paper, we extend this algorithmic question to deterministic automata beyond…

Formal Languages and Automata Theory · Computer Science 2020-12-23 Henning Fernau , Petra Wolf , Tomoyuki Yamakami

Good-for-MDPs and good-for-games automata are two recent classes of nondeterministic automata that reside between general nondeterministic and deterministic automata. Deterministic automata are good-for-games, and good-for-games automata…

Formal Languages and Automata Theory · Computer Science 2023-07-24 Sven Schewe , Qiyi Tang

We introduce exploration potential, a quantity that measures how much a reinforcement learning agent has explored its environment class. In contrast to information gain, exploration potential takes the problem's reward structure into…

Machine Learning · Computer Science 2016-11-21 Jan Leike

We study an expressive model of timed pushdown automata extended with modular and fractional clock constraints. We show that the binary reachability relation is effectively expressible in hybrid linear arithmetic with a rational and an…

Formal Languages and Automata Theory · Computer Science 2018-05-01 Lorenzo Clemente , Sławomir Lasota

We give extensional and intensional characterizations of functional programs with nondeterminism: as structure preserving functions between biorders, and as nondeterministic sequential algorithms on ordered concrete data structures which…

Logic in Computer Science · Computer Science 2023-06-22 James Laird

There are languages A such that there is a Pushdown Automata (PDA) that recognizes A which is much smaller than any Deterministic Pushdown Automata (DPDA) that recognizes A. There are languages A such that there is a Linear Bounded Automata…

Formal Languages and Automata Theory · Computer Science 2015-07-17 Richard Beigel , William Gasarch

A deterministic finite automaton in which every non-empty set of states occurs as the image of the whole state set under the action of a suitable input word is called completely reachable. We characterize such automata in terms of graphs…

Formal Languages and Automata Theory · Computer Science 2022-01-14 Evgeniya A. Bondar , David Casas , Mikhail V. Volkov

History-determinism is a restricted notion of nondeterminism in automata, where the nondeterminism can be successfully resolved based solely on the prefix read so far. History-deterministic automata still allow for exponential succinctness…

Formal Languages and Automata Theory · Computer Science 2026-05-28 Karoliina Lehtinen , Keya Prakash

In various models of one-way pushdown automata, the explicit use of two designated endmarkers on a read-once input tape has proven to be extremely useful for making a conscious, final decision on the acceptance/rejection of each input word…

Formal Languages and Automata Theory · Computer Science 2025-11-11 Tomoyuki Yamakami

A two-dimensional finite automaton has a read-only input head that moves in four directions on a finite array of cells labelled by symbols of the input alphabet. A three-way two-dimensional automaton is prohibited from making upward moves,…

Formal Languages and Automata Theory · Computer Science 2019-04-26 Taylor J. Smith , Kai Salomaa

A three-way (resp., two-way) two-dimensional automaton has a read-only input head that moves in three (resp., two) directions on a finite array of cells labelled by symbols of the input alphabet. Restricting the input head movement of a…

Formal Languages and Automata Theory · Computer Science 2021-05-05 Taylor J. Smith , Kai Salomaa

We show the diagonal problem for higher-order pushdown automata (HOPDA), and hence the simultaneous unboundedness problem, is decidable. From recent work by Zetzsche this means that we can construct the downward closure of the set of words…

Formal Languages and Automata Theory · Computer Science 2015-11-06 Matthew Hague , Jonathan Kochems , C. -H. Luke Ong