5,446 research outputs found
Cooperating Distributed Grammar Systems of Finite Index Working in Hybrid Modes
We study cooperating distributed grammar systems working in hybrid modes in
connection with the finite index restriction in two different ways: firstly, we
investigate cooperating distributed grammar systems working in hybrid modes
which characterize programmed grammars with the finite index restriction;
looking at the number of components of such systems, we obtain surprisingly
rich lattice structures for the inclusion relations between the corresponding
language families. Secondly, we impose the finite index restriction on
cooperating distributed grammar systems working in hybrid modes themselves,
which leads us to new characterizations of programmed grammars of finite index.Comment: In Proceedings AFL 2014, arXiv:1405.527
On the number of components in cooperating distributed grammar systems
AbstractIt is proved that the number of components in context-free cooperating distributed (CD) grammar systems can be reduced to 3 when they are working in the so-called sf-mode of derivation, which is the cooperation protocol which has been considered first for CD grammar systems. In this derivation mode, a component continues the derivation until and unless there is a nonterminal in the sentential form which cannot be rewritten according to that component. Moreover, it is shown that CD grammar systems in sf-mode with only one component can generate only the context-free languages but they can generate non-context-free languages if two components are used. The sf-mode of derivation is compared with other well-known cooperation protocols with respect to the hierarchies induced by the number of components
Uniform Distributed Pushdown Automata Systems.
We consider here uniform distributed pushdown automata systems (UDPAS), namely distributed pushdown automata systems having all components identical pushdown automata. We consider here just a single protocol for activating/deactivating components, namely a component stays active as long as it can perform moves, as well as two ways of accepting the input word: by empty stacks (all components have empty stacks) or by final states (all components are in final states), when the input word is completely read. We mainly investigate the computational power of UDPAS accepting by empty stacks and a few decidability and closure properties of the families of languages they define. Some directions for further work and open problems are also discussed
Array P Systems and t−Communication
The two areas of grammar systems and P systems, which have provided interesting computational models in the study of formal string language theory have been in the recent past
effectively linked in [4] by incorporating into P systems, a communication mode called t−mode of cooperating distributed grammar systems. On the other hand cooperating array grammar systems [5]and array P systems [1] have been developed in the context of two-dimensional picture description. In this paper, motivated by the study of [4], these two systems are studied by linking them through
the t−communication mode, thus bringing out the picture description power of these systems
Cooperating distributed grammar systems with random context grammars as components
In this paper, we discuss cooperating distributed grammar systems where components are (variants of) random context grammars. We give an overview of known results and open problems, and prove some further results
Systems of Sequential Grammars Applied to Parsing
Tato práce zkoumá Gramatické systémy jako potenciálně silnější nástroj pro syntaktickou analýzu, nežli obyčejné gramatiky. Hlavním záměrem je aplikace teoretických modelů do praxe, vytvoření syntaktického analyzátoru. Jsou zavedeny nové metody zaměřené na determinizmus, a tím vyhnutí se zpětnému navracení při analýze. Základem analyzátoru je CD gramatický systém. Implementace využívá metodu prediktivní syntaktické analýzy, překlad řízený tabulkou a také rekurzi. Analyzátor je univerzální, použitelný pro jakékoliv LL-Gramatiky a jakékoliv gramatické systémy na nich založené.This thesis examines Grammar systems as the potentially more powerful tool for parsing as the simple grammars. The intention is to adapt theoretical models of grammar systems for parsing. New methods are introduced, with focus on determinism in order to prevent backtracking during parsing. The basis for the parser is a cooperating distributed grammar system. The implementation uses predictive, top-down parsing method, LL(1)Tables, and recursion as well. The parser is universal, usable for any LL-Grammar and for any grammar system based on them.
Structuring grammar systems by priorities and hierarchies
A grammar system is a finite set of grammars that cooperate to generate a language. We consider two generalizations of grammar systems: (l) adding a priority relation between single grammar components, and (2) considering hierarchical components which by themselves are grammar systems. The generative power of these generalized grammar systems is investigated, and compared with the generative power of ordinary grammar systems and of some well-known types of grammars with regulated rewriting (such as matrix grammars). We prove that for many cooperating strategies the use of priority relation increases the generative capacity, however this is not the case for the maximal mode of derivation (an important case, because it gives a characterization of the ETOL languages). We also demonstrate that in many cases the use of hierarchical components does not increase the generative power
On Controlled P Systems
We introduce and brie
y investigate P systems with controlled computations.
First, P systems with label restricted transitions are considered (in each step, all
rules used have either the same label, or, possibly, the empty label, ), then P systems
with the computations controlled by languages (as in context-free controlled grammars).
The relationships between the families of sets of numbers computed by the various classes
of controlled P systems are investigated, also comparing them with length sets of languages
in Chomsky and Lindenmayer hierarchies (characterizations of the length sets of
ET0L and of recursively enumerable languages are obtained in this framework). A series
of open problems and research topics are formulated
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