We consider finite and polynomial ambiguity of weighted tree automata. Concerning finite ambiguity, we show that a finitely ambiguous weighted tree automaton can be decomposed into a sum of unambiguous automata. For polynomial ambiguity, we show how to decompose a polynomially ambiguous weighted tree automaton into simpler polynomially ambiguous automata and then analyze the structure of these ...

We introduce the separable sets of variables for trees and tree au-tomata. If a set Y of input variables is inseparable for a tree and an automaton then there a non empty family of distributive sets of Y. It is shown that if a tree t has " many " inseparable sets with respect to a tree automaton A then there is an effective way to reduce the complexity of A when running on t.

When reading an input tree, a bottom-up tree automaton is \unaware" of where it is relative to the root. This problem is important to the eecient implementation of decision procedures for the Monadic Second-order Logic (M2L) on nite trees. In 7], it is shown how exponential state space blow-ups may occur in common situations. The analysis of the problem leads to the notion of guided tree automa...

This paper introduces and discusses pure multi-pushdown automata that remove symbols from their pushdowns only by performing complete-pushdown pops. During this operation, the entire pushdown is compared with a prefix of the input, and if they match, the pushdown is completely emptied and the input is advanced by the prefix. The paper proves that these automata define an infinite hierarchy of l...

This paper presents some results of an attempt to develop a common parsing scheme that works systematically and realistically for typologically varied natural languages. The scheme is bottom-up, and the parser scans the input text from left to right. However, unlike the standard LR(k) parser or Tomita's extended LR(1) parser, the one presented in this paper is not a pushdown automaton based on ...

ion Refinement and Antichains for Trace Inclusion of Infinite State Systems Radu Iosif, Adam Rogalewicz, and Tomáš Vojnar CNRS/Verimag, France and FIT BUT, Czech Republic Abstract. A data automaton is a finite automaton equipped with variables (counA data automaton is a finite automaton equipped with variables (counters or registers) ranging over infinite data domains. A trace of a data automat...

The word position automaton was introduced by Glushkov and McNaughton in the early 1960. This automaton is homogeneous and has (||E || + 1) states for a word expression of alphabetic width ||E ||. This kind of automata is extended to regular tree expressions. In this paper, we give an efficient algorithm that computes the Follow sets, which are used in different algorithms of conversion of a re...

In this paper, we extend the notion of tree language quotients to bottom-up quotients. Instead of computing the residual of a tree language from top to bottom and producing a list of tree languages, we show how to compute a set of k-ary trees, where k is an arbitrary integer. We define the quotient formula for different combinations of tree languages: union, symbol products, compositions, itera...

We present the STack ARchitecture (STAR) automaton. It is a fixed structure, multiaction, reward-penalty learning automaton, characterized by a star-shaped state transition diagram. Each branch of the star contains D states associated with a particular action. The branches are connected to a central "neutral" state. The most general version of STAR involves probabilistic state transitions in re...

Timed-Arc Petri Nets (TAPN) are an extension of the classical P/T nets with continuous time. Tokens in TAPN carry an age and arcs between places and transitions are labelled with time intervals restricting the age of tokens available for transition firing. The TAPN model posses a number of interesting theoretical properties distinguishing them from other time extensions of Petri nets. We shall ...