We study several extensions of the notion of alternation from context-free grammars to context-sensitive and arbitrary phrase-structure grammars. Thereby new grammatical characterizations are obtained for the class of languages that are accepted by alternating pushdown automata.

We consider the emptiness problem for alternating tree automata, with two acceptance semantics: classical (all branches are accepted) and qualitative (almost all branches are accepted). For the classical semantics, the usual technique to tackle this problem relies on a Simulation Theorem which constructs an equivalent non-deterministic automaton from the original alternating one, and then check...

We consider co–Büchi tree automata along with both alternating and generalized paradigms, as a characterization of the class of languages whose complement is accepted by generalized Büchi tree automata. We first prove that for alternating generalized co–Büchi tree automata the simulation theorem does not hold and the generalized acceptance does not add to the expressive power of the model. Then...

Article history: Received 23 December 2009 Received in revised form 3 April 2013 Available online 18 April 2014

The field of finite tree automata provides fundamental notations and tools for reasoning about set of terms called regular or recognizable tree languages. We consider two kinds of analysis using regular tree languages, applied to logic programs. The first approach is to try to discover automatically a tree automaton from a logic program, approximating its minimal Herbrand model. In this case th...

Abstract. We consider multi-pushdown automata, a multi-stack extension of pushdown automata that comes with a constraint on stack operations: a pop can only be performed on the first non-empty stack (which implies that we assume a linear ordering on the collection of stacks). We show that the emptiness problem for multi-pushdown automata is 2ETIME-complete wrt. the number of stacks. Containment...

Weakly definable languages of infinite trees are an expressive subclass of regular tree languages definable in terms of weak monadic second-order logic, or equivalently weak alternating automata. Our main result is that given a Büchi automaton, it is decidable whether the language is weakly definable. We also show that given a parity automaton, it is decidable whether the language is recognizab...

We present an extension of the learning classifier system XCS in which classifier conditions are represented by RPN expressions and stack-based Genetic Programming is used to recombine and mutate classifiers. In contrast with other extensions of XCS involving tree-based Genetic Programming, the representation we apply here produces conditions that are linear programs, interpreted by a virtual s...

In this paper, we focus on solving games in recursive game graphs that can model the control flow of sequential programs with recursive procedure calls. The winning condition is given as an ω-regular specification over the observable, and, unlike traditional pushdown games, the strategy is required to be modular: resolution of choices within a component should not depend on the context in which...

Alternating automata on infinite trees induce operations on languages which do not preserve natural equivalence relations, like having the same Mostowski–Rabin index, the same Borel rank, or being continuously reducible to each other (Wadge equivalence). In order to prevent this, alternation needs to be restricted to the choice of direction in the tree. For weak alternating automata with restri...