Showing papers on "Indexed language published in 1996"
TL;DR: A new class of languages, called multi-push-down (mpd), that generalize the classical context-free ones (cf, or Chomsky type 2) and preserve some important properties of classical languages.
Abstract: A new class of languages, called multi-push-down (mpd), that generalize the classical context-free (cf, or Chomsky type 2) ones is introduced. These languages preserve some important properties of ...
113 citations
TL;DR: In this article, the fundamental group of every compact 3-manifold which satisfies Thurston's geometrization conjecture is defined and studied, and the class of asynchronously automatic groups is introduced and studied.
Abstract: Automatic groups were introduced in connection with geometric problems, in particular with the study of fundamental groups of 3-manifolds. In this article the class of automatic groups is extended to include the fundamental group of every compact 3-manifold which satisfies Thurston's geometrization conjecture. Toward this end, the class
of asynchronously
groups is introduced and studied, where
is an arbitrary full abstract family of languages. For example
may be the family of regular languagesReg, context-free languagesCF, or indexed languagesInd. The class
consists of precisely those groups which are asynchronously automatic. It is proved that
contains all of the above fundamental groups, but that
does not. Indeed a virtually nilpotent group belongs to
if and only if it is virtually abelian.
50 citations
TL;DR: The paper provides an accurate analysis of the derivation mechanism and the expressive power of the SR formalism, which is necessary to fully exploit the capabilities of the model.
Abstract: A common approach to the formal description of pictorial and visual languages makes use of formal grammars and rewriting mechanisms. The present paper is concerned with the formalism of Symbol?Relation Grammars (SR grammars, for short). Each sentence in an SR language is composed of a set of symbol occurrences representing visual elementary objects, which are related through a set of binary relational items. The main feature of SR grammars is the uniform way they use context-free productions to rewrite symbol occurrences as well as relation items. The clearness and uniformity of the derivation process for SR grammars allow the extension of well-established techniques of syntactic and semantic analysis to the case of SR grammars. The paper provides an accurate analysis of the derivation mechanism and the expressive power of the SR formalism. This is necessary to fully exploit the capabilities of the model. The most meaningful features of SR grammars as well as their generative power are compared with those of well-known graph grammar families. In spite of their structural simplicity, variations of SR grammars have a generative power comparable with that of expressive classes of graph grammars, such as the edNCE and the N-edNCE classes.
43 citations
TL;DR: A lemma in the spirit of the pumping lemma for indexed languages but easier to employ is presented, which can be applied to types of indexed languages.
39 citations
TL;DR: An infinite hierarchy of languages that comprises the context-free languages as the first and all the languages generated by Tree Adjoining Grammars (TAGs) as the second element is obtained.
27 citations
TL;DR: Here a polynomial-time parsing algorithm fork-depth languages is defined, and its correctness is proved.
7 citations
17 Sep 1996
TL;DR: The mildly context-sensitiveness property, the possibility to cover certain constructions specific to natural languages, as well as the ambiguity of languages generated by the grammars are discussed.
Abstract: We continue here the investigations concerning the relevance of certain classes of contextual grammars (internal contextual grammars with maximal use of selectors) as generative models of natural languages. We discuss the mildly context-sensitiveness property (especially the semilinearity and related properties), the possibility to cover certain constructions specific to natural languages, as well as the ambiguity of languages generated by our grammars. Then, contextual grammars with the selectors presented as patterns are introduced and briefly investigated from the point of view of covering the mentioned constructions in natural languages.
3 citations
TL;DR: It is shown that context‐sensitive languages exist which can be generated by context‐free parallel grammars, and that CFPL is a more effective tool for modelling computer programming languages than CFL, especially for parallelComputer programming languages, for example, the ADA programming language.
Abstract: Describes intuitively the fact that four types of formal languages can be generated by four types of grammars or can be recognized by four types of automata. Gives the relationships between context‐sensitive languages and computer programming languages. Defines and investigates parallel productions, parallel grammars, and context‐free parallel grammars. Shows that context‐sensitive languages exist which can be generated by context‐free parallel grammars. In addition, states the advantages of context‐free parallel grammars. Also shows that context‐free languages (CFL) are a proper subset of context‐free parallel languages (CFPL). Furthermore, CFPL is a more effective tool for modelling computer programming languages than CFL, especially for parallel computer programming languages, for example, the ADA programming language. Also illustrates context‐sensitive property of recognizing hand‐written characters. The results may have useful applications in artificial intelligence, model parallel computer programming languages, software engineering, expert systems and robotics.
1 citations