This paper provides an algorithm to compute the complement of tree languages recognizable with A-TA (tree automata with associativity axioms [16]). Due to this closure property together with the previously obtained results, we know that the class is boolean closed, while keeping recognizability of A-closures of regular tree languages. In the proof of the main result, a new framework of tree aut...

We investigate properties of node centrality in random growing tree models. We focus on a measure of centrality that computes the maximum subtree size of the tree rooted at each node, with the most central node being the tree centroid. For random trees grown according to a preferential attachment model, a uniform attachment model, or a diffusion processes over a regular tree, we prove that a si...

We investigate rational relations over trees. Our starting point is the definition of rational tree relations via rational expressions byRaoult (Bull. Belg.Math. Soc. 1997). We develop a new class of automata, called asynchronous tree automata, which recognize exactly these relations. The automata theoretic approach is convenient for the solution of algorithmic problems (like the emptiness prob...

Algorithms for validation play a crucial role in the use of XML. Although much effort has been made for formalizing the treatment of elements, attributes have been neglected. This paper presents a validation model for XML documents that takes into account element and attribute constraints imposed by a given DTD. Our main contribution is the introduction of a new formalism to deal with both kind...

A software system called Treebag|Tree-Based G enerator|is presented. The aim behind Treebag is to allow for the generation and visualization of objects of all kinds: pictures, trees, graphs, strings, numbers, etc. The basic principle is that tree generators like, for instance, regular tree grammars, generate terms over symbols that are interpreted by appropriate algebras as operations on the do...

We develop a general framework for weighted parsing which is built on top of grammar-based language models and employs multioperator monoids (M-monoids) as weight algebras. It generalizes previous work in that area, e.g., semiring deductive parsing, also covers applications outside the classical scope algebraic dynamic programming. More specifically, we introduce RTG-based (where RTG stands reg...

I n t r o d u c t i o n In [9] a comparison was made of the generative capacity of a number of grammar formalisms. Several were found to share a number of characteristics (described below) and the class of such formalisms was called linear context-free rewriting systems. This paper shows how the class of string languages generated by linear context-free rewriting systems relates to a number of ...

Minimalist Grammars (MGs) (Stabler, 1997) are a formalisation of Chomsky’s minimalist program (Chomsky, 1995), which currently dominates much of mainstream syntax. MGs are simple and intuitive to work with, and are mildly context sensitive (Michaelis, 1998), putting them in the right general class for human language (Joshi, 1985).1 Minimalist Grammars are known to be more succinct than their Mu...

We study the problem of learning regular tree languages from text. We show that the framework of function distinguishability as introduced by the author in Theoretical Computer Science, 290:1679–1711, 2003, can be generalized from the case of string languages towards tree languages. This provides a large source of identifiable classes of regular tree languages. Each of these classes can be char...

Significant progress in the area of formal tools to support the construction of code generators in recent years has come along with a severe terminological confusion. Closely related techniques appear in different styles, further obscured by ad-hoc extensions. We try to alleviate this situation by suggesting that the code selection task should be understood as the problem of inversion of a hier...