Showing papers on "Context-sensitive grammar published in 1985"
TL;DR: What is currently known about natural language morphology and syntax from the perspective of formal language theory is surveyed and recent developments such as feature-theory, the use of extension and unification, default mechanisms, and metagram-matical techniques are outlined.
Abstract: This paper surveys what is currently known about natural language morphology and syntax from the perspective of formal language theory. Firstly, the position of natural language word-sets and sentence-sets on the formal language hierarchy is discussed. Secondly, the contemporary use by linguists of a range of formal grammars (from finite state transducers to indexed grammars) in both word-syntax (i.e. morphology) and sentence-syntax is sketched. Finally, recent developments such as feature-theory, the use of extension and unification, default mechanisms, and metagram-matical techniques, are outlined.
55 citations
TL;DR: It is proved that semi-conditional grammars with very short conditions w1, w2 characterize the context-sensitive languages (recursively enumerable languages when λ-rules are allowed).
48 citations
46 citations
TL;DR: It is proved that the class of NTS grammars has an undecidable inclusion problem and it is shown that one can decide whether a given c.f. grammar is NTS or not.
40 citations
TL;DR: It is shown that the inequivalence problems for type 0 and context-sensitive commutative grammars are undecidable whereas decidability in nondeterministic exponential-time holds for the classes of regular and contextually-free Commutative Grammars.
Abstract: In this paper we investigate the computational complexity of the inequivalence problems for commutative grammars. We show that the inequivalence problems for type 0 and context-sensitive commutative grammars are undecidable whereas decidability in nondeterministic exponential-time holds for the classes of regular and context-free commutative grammars. For the latter the inequivalence problems are Σp2-hard.
35 citations
TL;DR: The use of graph grammars for specifying (generating) languages of dependency graphs that arise in theoretical studies of concurrent systems is pointed out.
16 citations
TL;DR: An extensive number of examples are given which illustrate how a quite considerable number of grammars and automata considered in the literature may be ‘naturally’ interpreted as special instances (subclasses of the class) of cts systems.
9 citations
TL;DR: An extended version of the parallel/sequential table matrix models called extended table matrix grammars (Ex-TMG), generating arrays of symbols, is proposed, and the notion of assigning “terminal weights” to matrix Grammars for describing parquet deformations is extended to Ex-TMGs.
9 citations
TL;DR: Szilard languages and label languages are studied as examples of languages generable by permutative grammars, particularly, sufficient conditions for apermutative grammar to generate a context-free language.
Abstract: A grammar is said to be permutative if it has permutation productions of the formAB ρBA in addition to context-free productions. Szilard languages and label languages are studied as examples of languages generable by permutative grammars. Particularly, sufficient conditions for a permutative grammar to generate a context-free language are studied.
8 citations
TL;DR: It is proved that a language is generated by a 1S grammar if and only if it is context-free: this solves an open problem from the theory of selective substitution grammars.
01 Apr 1985-Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing
TL;DR: A terminal weighted grammar is defined, where the terminal generated at any step of a derivation is defined as a function of time, and it is seen that terminal weighted regular grammars generate exactly the class of recursively enumerable sets.
Abstract: Motivated by the idea of describing parquet deformations using grammars and also of describing an infinite number of terminals starting with only a finite set, this paper defines a terminal weighted grammar, where the terminal generated at any step of a derivation is defined as a function of time It is seen that terminal weighted regular grammars generate exactly the class of recursively enumerable sets Terminal weighted matrix grammars are used to describe parquet deformations The extension of terminal weights to array grammars is also discussed
TL;DR: These results provide a rare example of a nontrivial natural algebraic and/or combinatorial structure, namely the unambiguous context-free grammars, with polynomial time algorithms for homomorphism, onto homomorphicism, and isomorphism.
TL;DR: Two constructions of generalized Grammars are investigated and families of languages are studied for which these constructions provide grammars.
Abstract: Two constructions of generalized grammars are investigated and families of languages are studied for which these constructions provide grammars. One of these families coincides with the family of linear languages, another includes the family of linear deterministic languages and the family of contextual languages.
Proceedings Article•
18 Aug 1985TL;DR: A Flexible Implementation of Gapping Grammars, a large subset of unrestricted GGs which allows either bottom-up or top-down parsing of sentences, and provides more built in control facilities than previous logic grammar implementations.
Abstract: Since the introduction of metamorphosis grammars (MGs) 'Colmerauer. 1978). with their associated type O-like grammar rules, there has been a desire to allow more general rule formats in logic grammars Gaps, which refer to strings of unspecified symbols, were added to the MG rule, resulting in extraposition grammars (XGs) (Pereira, 1981) and gapping grammars (GGs) (Dahl and Abramson, 1984). Unrestricted gapping grammars, which provide an even more general rule format, possess rules of the form "a - > B" where a and /3 many contain any number of terminal nonterminal or gap symbols in any order. FIGG. a Flexible Implementation of Gapping Grammars, is an implementation of a large subset of unrestricted GGs which allows either bottom-up or top-down parsing of sentences. This system provides more built in control facilities than previous logic grammar implementations, which allows the user to restrict the applicability of the rules, and to create grammar rules that will be executed more efficiently
09 Sep 1985
TL;DR: It is shown that even linear and deterministic context-free languages can generate languages of multisets, the membership problem of which is NP-complete in DSPACE(log n) for regular sets.
Abstract: The complexity of languages generated by context-free grammars with disconnecting is investigated. It is shown that even linear and deterministic context-free languages can generate languages of multisets, the membership problem of which is NP-complete. In contrast to that, this problem is in DSPACE(log n) for regular sets.
03 Jan 1985
TL;DR: This paper shows that the characterization of fairly terminating grammars as non-variable-doubling is valid under canonical derivations in which the next variable to be expanded is deterministically chosen, leaving nondeterminism only to the decision as to which rule to apply.
Abstract: In [PFMZ 82] the notion of Fair derivations in context free grammars was introduced and studied The main result there is a characterization of fairly terminating grammars as non-variable-doubling In this paper we show that the same characterization is valid under canonical derivations in which the next variable to be expanded is deterministically chosen, leaving nondeterminism only to the decision as to which rule to apply Two families of canonical derivations are introduced and studied: 1) Spinal derivations and 2) Layered derivations
01 Jan 1985
TL;DR: An extensive number of examples are given which illustrate how a quite considerable number of grammars and automata considered in the literature may be 'naturally' interpreted as special instances (subclasses of the class) of cts systems.
Abstract: The notion of a coordinated table selective substitution system (acts system) is introduced. It provides a unifying framework for both grammars and machines (automata) and hence a really broad framework for formal language theory. An extensive number of examples is given which illustrate how a quite considerable number of grammars and automata considered in the literature may be 'naturally' interpreted as special instances (subclasses of the class) of cts systems.
TL;DR: General one-pass grammars can be evaluated using recursive procedures in the same way as forL-attributed Grammars, provided that call-by-name parameters are available.
Abstract: An attribute grammar is considered to be one-pass if all the attribute instances of any derivation tree can be evaluated by a process that traverses the tree from left to right visiting each subtree at most once. It is shown that this general class of one-pass grammars properly includesL-attributed grammars; in fact,L-attributed grammars can be viewed as a practical subset of the general class. General one-pass grammars can be evaluated using recursive procedures in the same way as forL-attributed grammars, provided that call-by-name parameters are available.