Alexandru Mateescu

Bio: Alexandru Mateescu is an academic researcher from University of Bucharest. The author has contributed to research in topics: Formal language & Context-sensitive grammar. The author has an hindex of 16, co-authored 70 publications receiving 1079 citations. Previous affiliations of Alexandru Mateescu include University of Turku & Turku Centre for Computer Science.

A sharpening of the Parikh mapping

Abstract: In this paper we introduce a sharpening of the Parikh map- ping and investigate its basic properties. The new mapping is based on square matrices of a certain form. The classical Parikh vector appears in such a matrix as the second diagonal. However, the matrix prod- uct gives more information about a word than the Parikh vector. We characterize the matrix products and establish also an interesting in- terconnection between mirror images of words and inverses of matrices. Mathematics Subject Classification. 68Q45, 68Q70.

Aspects of classical language theory

Abstract: The purpose of this chapter is to give an overview on some types of grammars and families of languages arising in classical language theory and not covered elsewhere in this Handbook. Since we will discuss in this chapter a large number of topics, we cannot penetrate very deeply in any one of them. Topics very related to the ones discussed in this chapter, such as regular languages and context-free languages, have their own chapters in this Handbook, where the presentation is more detailed than in the present chapter. Among the topics covered in this chapter (Section 3 below) will also be the general theory of language families, AFL-theory. In view of the whole language theory, there is a huge number of topics possible for this chapter. It is clear that our choice of topics and the amount of detail in which each of them is presented reflect, at least to some extent, our personal tastes.

Formal languages: an introduction and a synopsis

Abstract: What is a language? By consulting a dictionary one finds, among others, the following explanations: 1 The body of words and systems for their use common to people who are of the same community or nation, the same geographical area, or the same cultural tradition. 2 Any set or system of signs or symbols used in a more or less uniform fashion by a number of people who are thus enabled to communicate intelligibly with one other. 3 Any system of formalized symbols, signs, gestures, or the like, used or conceived as a means of communicating thought, emotion, etc.

Tree Automata Techniques and Applications

Abstract: CONTENTS 7 Acknowledgments Many people gave substantial suggestions to improve the contents of this book. These are, in alphabetic order, Introduction During the past few years, several of us have been asked many times about references on finite tree automata. On one hand, this is the witness of the liveness of this field. On the other hand, it was difficult to answer. Besides several excellent survey chapters on more specific topics, there is only one monograph devoted to tree automata by Gécseg and Steinby. Unfortunately, it is now impossible to find a copy of it and a lot of work has been done on tree automata since the publication of this book. Actually using tree automata has proved to be a powerful approach to simplify and extend previously known results, and also to find new results. For instance recent works use tree automata for application in abstract interpretation using set constraints, rewriting, automated theorem proving and program verification, databases and XML schema languages. Tree automata have been designed a long time ago in the context of circuit verification. Many famous researchers contributed to this school which was headed by A. Church in the late 50's and the early 60's: B. Trakhtenbrot, Many new ideas came out of this program. For instance the connections between automata and logic. Tree automata also appeared first in this framework, following the work of Doner, Thatcher and Wright. In the 70's many new results were established concerning tree automata, which lose a bit their connections with the applications and were studied for their own. In particular, a problem was the very high complexity of decision procedures for the monadic second order logic. Applications of tree automata to program verification revived in the 80's, after the relative failure of automated deduction in this field. It is possible to verify temporal logic formulas (which are particular Monadic Second Order Formulas) on simpler (small) programs. Automata, and in particular tree automata, also appeared as an approximation of programs on which fully automated tools can be used. New results were obtained connecting properties of programs or type systems or rewrite systems with automata. Our goal is to fill in the existing gap and to provide a textbook which presents the basics of tree automata and several variants of tree automata which have been devised for applications in the aforementioned domains. We shall discuss only finite tree automata, and the …

Tissue P systems

Abstract: Starting from the way the inter-cellular communication takes place by means of protein channels (and also from the standard knowledge about neuron functioning), we propose a computing model called a tissue P system, which processes symbols in a multiset rewriting sense, in a net of cells. Each cell has a finite state memory, processes multisets of symbol-impulses, and can send impulses (“excitations”) to the neighboring cells. Such cell nets are shown to be rather powerful: they can simulate a Turing machine even when using a small number of cells, each of them having a small number of states. Moreover, in the case when each cell works in the maximal manner and it can excite all the cells to which it can send impulses, then one can easily solve the Hamiltonian Path Problem in linear time. A new characterization of the Parikh images of ET0L languages is also obtained in this framework. Besides such basic results, the paper provides a series of suggestions for further research.

Grammar Systems: A Grammatical Approach to Distribution and Cooperation

Abstract: From the Publisher: This book investigates two major systems: firstly, cooperating distributed grammar systems, where the grammars work on one common sequential form and the cooperation is realized by the control of the sequence of active grammars; secondly, parallel communicating grammar systems, where each grammar works on its own sequential form and cooperation is done by means of communicating between grammars. The investigation concerns hierarchies with respect to different variants of cooperation, relations with classical formal language theory, syntactic parameters such as the number of components and their size, power of synchronization, and general notions generated from artificial intelligence.

Synchronizing Automata and the Černý Conjecture

Abstract: We survey several results and open problems related to synchronizing automata. In particular, we discuss some recent advances towards a solution of the Cerný conjecture.