Showing papers by "Grzegorz Rozenberg published in 1984"
TL;DR: It is shown that it is decidable whether an arbitrary DOL language is repetitive and it is also shown that if a DOLlanguage is repetitive then it is strongly repetitive.
Abstract: A language K ⊆ Σ * is repetitive if for each positive integer n there exists a word w ∈ Σ + such that w n is a subword of K . Language K is called strongly repetitive if there exists a word w ∈ Σ + , such that, for each positive integer n , w n is a subword of K . It is shown that it is decidable whether an arbitrary DOL language is repetitive. It is also shown that if a DOL language is repetitive then it is strongly repetitive.
31 citations
TL;DR: This paper examines certain restrictions on NLC grammars similar to the Chomsky or Greibach normal forms for context-free string Grammars, and finds that each of the restrictions causes a reduction in generating power for the grammar.
28 citations
TL;DR: In this paper, a sufficient condition for a copy language to be regular is provided; an application of this condition is demonstrated in the context of regular copy language construction, where the copying relation copy∗ is defined as the reflexive and transitive closure of copy, and a copying system is an ordered pair G = (Σ, w) where w ϵΣ+; its language is L(G) = {zϵ Σ + : w copy ∗ z}, it is referred to as a copy languages.
27 citations
01 Jan 1984
TL;DR: In this article, it was shown that it is decidable whether or not the language of an arbitrary node label controlled (NLC) grammar is of bounded degree and, given an arbitrary NLC grammar G, one can effectively compute the maximum integer which appears as the degree of a graph in L(G).
Abstract: Abstract The degree of a graph H is the maximum among the degrees of its nodes. A set of graphs L is of bounded degree if there exists a positive integer n such that the degree of each graph in L does not exceed n . We demonstrate that it is decidable whether or not the (graph) language of an arbitrary node label controlled (NLC) grammar is of bounded degree. Moreover, it is shown that, given an arbitrary NLC grammar G generating the language L(G) of bounded degree, one can effectively compute the maximum integer which appears as the degree of a graph in L(G) .
21 citations
TL;DR: It is proved that every commutative one-counter language is regular and a new characterization of commUTative regular languages is given.
16 citations
TL;DR: Dans cet article, le rapport entre 2 lignes du developpement a l'interieur de la theorie des grammaires de graphes est discute.
5 citations
TL;DR: An algebraic characterization of a fundamental subclass of theDOS mappings generated byDOS schemes which are propagating and have no cycles of derivability among letters of the alphabet is obtained to show that the mapping equivalence problem for propagatingDOS schemes is decidable.
Abstract: Roughly speaking,DOS systems formalize the notion of generatively deterministic context free grammars. We explore the containment relationships among the class of languages generated byDOS systems and other subclasses of the class of context free languages. Leaving the axiom of aDOS system unspecified yields aDOS scheme, which defines a mapping from words to languages over a given alphabet. We explore the algebraic properties ofDOS mappings and obtain an algebraic characterization of a fundamental subclass of theDOS mappings generated byDOS schemes which are propagating (non erasing) and have no cycles of derivability among letters of the alphabet. We apply this characterization to show that the mapping equivalence problem for propagatingDOS schemes is decidable.
2 citations
TL;DR: On montre que certains resultats (trouves ici) d'indecidabilite sont en fait vrais pour une sous-classe stricte de la classe des systemes DOS.
Abstract: Cet article etudie le concept d'ambiguite dans les systemes DOS; on s'interesse tout particulierement aux problemes de decision lies a l'ambiguite dans les systemes DOS. On montre que certains resultats (trouves ici) d'indecidabilite sont en fait vrais pour une sous-classe stricte de la classe des systemes DOS (langages) definie par restriction aux systemes DOS acycliques et propageants
TL;DR: It is proved that for each synchronized EOL form a propagating E OL form can be constructed with the same n -family.