In this paper we present Regular XPath (RXPath), which is a natural extension of XPath with regular expressions over paths that has the same computational properties as XPath: linear-time query evaluation and exponential-time reasoning. To establish these results, we devise a unifying automata-theoretic framework based on two-way weak alternating tree automata. Specifically, we consider automat...

The unsupervised Data Oriented Parsing (uDOP) approach has been repeatedly reported to achieve state of the art performance in experiments on parsing of different corpora. At the same time the approach is demanding both in computation time and memory. This paper describes an approach which decreases these demands. First the problem is translated into the generation of probabilistic bottom up tr...

In this paper, we present VATA, a versatile and efficient open-source tree automata library applicable, e.g., in formal verification. The library supports both explicit and semi-symbolic encoding of non-deterministic finite tree automata and provides efficient implementation of standard operations on both. The semi-symbolic encoding is intended for tree automata with large alphabets. For storin...

Tree automata have been defined to accept trees. Different types of acceptance like bottom-up, top-down, tree walking have been considered in the literature. In this paper, we consider bottom-up tree automata and discuss the sequential distributed version of this model. Generally, this type of distribution is called cooperative distributed automata or the blackboard model. We define the traditi...

We develop an automata-theoretic framework for reasoning about linear properties of infinite-state sequential systems. Our framework is based on the observation that states of such systems, which carry a finite but unbounded amount of information, can be viewed as nodes in an infinite tree, and transitions between states can be simulated by finite-state automata. Checking that the system satisf...

In this paper, at first we define the concepts of response function and accessible states of a complete residuated lattice-valued (for simplicity we write $mathcal{L}$-valued) tree automaton with a threshold $c.$ Then, related to these concepts, we prove some lemmas and theorems that are applied in considering some decision problems such as finiteness-value and emptiness-value of recognizable t...

We introduce a new syntax-directed translation device called top-down tree-to-graph transducer. Such transducers are very similar to the usual (total deterministic) top-down tree transducers except that the right-hand sides of their rules are hypergraphs rather than trees. Since we are aiming at a device which also allows us to translate trees into objects different from graphs, we focus our at...