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We present an efficient algorithm for checking language equivalence of states in top-down deterministic finite tree automata (DFTAs). Unlike string automata, tree automata operate over hierarchical structures, posing unique challenges for…

Formal Languages and Automata Theory · Computer Science 2025-04-08 Zhibo Deng , Vladimir A. Zakharov

We consider pushdown timed automata (PTAs) that are timed automata (with dense clocks) augmented with a pushdown stack. A configuration of a PTA includes a control state, dense clock values and a stack word. By using the pattern technique,…

Logic in Computer Science · Computer Science 2007-05-23 Zhe Dang

We introduce deterministic suffix-reading automata (DSA), a new automaton model over finite words. Transitions in a DSA are labeled with words. From a state, a DSA triggers an outgoing transition on seeing a word ending with the…

Formal Languages and Automata Theory · Computer Science 2026-05-13 R Keerthan , B Srivathsan , R Venkatesh , Sagar Verma

We introduce deterministic suffix-reading automata (DSA), a new automaton model over finite words. Transitions in a DSA are labeled with words. From a state, a DSA triggers an outgoing transition on seeing a word ending with the…

Formal Languages and Automata Theory · Computer Science 2024-10-31 R Keerthan , B Srivathsan , R Venkatesh , Sagar Verma

In (Csuhaj-Varju et. al. 2000) Parallel Communicating Systems of Pushdown Automata (PCPA) were introduced and shown to be able to simulate nondeterministic one-way multi-head pushdown automata in returning mode, even if communication is…

Formal Languages and Automata Theory · Computer Science 2014-08-07 Holger Petersen

In this tutorial, we illustrate through examples how we can combine two classical models, namely those of pushdown automata (PDA) and timed automata, in order to obtain timed pushdown automata (TPDA). Furthermore, we describe how the…

Logic in Computer Science · Computer Science 2012-12-18 Parosh Aziz Abdulla , Mohamed Faouzi Atig , Jari Stenman

In this paper, we introduce rerailing automata for $\omega$-regular languages. They generalize both deterministic parity (DPW) and minimized history-deterministic co-B\"uchi automata (with transition based acceptance, HdTbcBW) while…

Formal Languages and Automata Theory · Computer Science 2025-03-12 Rüdiger Ehlers

A discounted-sum automaton (NDA) is a nondeterministic finite automaton with edge weights, valuing a run by the discounted sum of visited edge weights. More precisely, the weight in the i-th position of the run is divided by $\lambda^i$,…

Formal Languages and Automata Theory · Computer Science 2015-07-01 Udi Boker , Thomas A. Henzinger

We show that every two-way deterministic finite automaton (2DFA) that solves one-way liveness on height h has Omega(h^2) states. This implies a quadratic lower bound for converting one-way nondeterministic finite automata to 2DFAs, which…

Formal Languages and Automata Theory · Computer Science 2026-03-02 Kehinde Adeogun , Christos Kapoutsis

We present an algorithm which modifies a deterministic pushdown automaton (DPDA) such that (i) the marked language is preserved, (ii) lifelocks are removed, (iii) deadlocks are removed, (iv) all states and edges are accessible, and (v)…

Formal Languages and Automata Theory · Computer Science 2014-03-24 Sven Schneider , Uwe Nestmann

Parikh (tree) automata are an expressive and yet computationally well-behaved extension of finite automata -- they allow to increment a number of counters during their computations, which are finally tested by a semilinear constraint. In…

Formal Languages and Automata Theory · Computer Science 2024-09-12 Luisa Herrmann , Johannes Osterholzer

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

The linear-time simulation of 2-way deterministic pushdown automata (2DPDA) by the Cook and Jones constructions is revisited. Following the semantics-based approach by Jones, an interpreter is given which, when extended with random-access…

Programming Languages · Computer Science 2013-09-23 Robert Glück

Various variants of Parikh automata on infinite words have recently been introduced in the literature. However, with some exceptions only their non-deterministic versions have been considered. In this paper we study the deterministic…

Formal Languages and Automata Theory · Computer Science 2024-05-27 Mario Grobler , Sebastian Siebertz

In the process of code generation, it is essential to guarantee the generated code satisfies grammar constraints of programming language (PL). However, neglecting grammar constraints is a fatal drawback of commonly used sequence-based code…

Software Engineering · Computer Science 2023-01-18 Yihong Dong , Xue Jiang , Yuchen Liu , Ge Li , Zhi Jin

A fundamental question in logic and verification is the following: for which unary predicates $P_1, \ldots, P_k$ is the monadic second-order theory of $\langle \mathbb{N}; <, P_1, \ldots, P_k \rangle$ decidable? Equivalently, for which…

Formal Languages and Automata Theory · Computer Science 2025-06-24 Valérie Berthé , Toghrul Karimov , Mihir Vahanwala

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

This paper studies the complexity of operations on finite automata and the complexity of their decision problems when the alphabet is unary. Let $n$ denote the maximum of the number of states of the input finite automata considered in the…

Formal Languages and Automata Theory · Computer Science 2024-12-16 Wojciech Czerwiński , Maciej Dębski , Tomasz Gogasz , Gordon Hoi , Sanjay Jain , Michał Skrzypczak , Frank Stephan , Christopher Tan

Families of DFAs (FDFAs) provide an alternative formalism for recognizing $\omega$-regular languages. The motivation for introducing them was a desired correlation between the automaton states and right congruence relations, in a manner…

Formal Languages and Automata Theory · Computer Science 2023-06-22 Dana Angluin , Udi Boker , Dana Fisman

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