Contextual Grammars Research Articles

Syntactic complexity of scattered context grammars

The syntactic complexity of scattered context grammars with respect to the number of nonterminals is investigated. First, the family of the recursively enumerable languages is characterized by some basic operations, such as quotient and coding, over the languages generated by propagating scattered context grammars with four nonterminals. Then, a new method of achieving the characterization of the family of recursively enumerable languages by scattered context grammars is given; in fact, this family is characterized by scattered context grammars with only five nonterminals and a single erasing production. Finally, it is demonstrated that the number of nonterminals can be decreased by one in the present characterizations if scattered context grammars start their derivations from a word rather than a single symbol.

Syntactic complexity of scattered context grammars

Syntactic complexity of scattered context grammars

Chart parsing of scattered context grammars

Scattered context grammars are a class of context-sensitive grammars. The rules of these grammars can be viewed as sequences of traditional context-free grammar rules. We show how a chart-parsing algorithm for context-free grammars can be extended to scattered context grammars.

GRAMMARS BASED ON PATTERNS

Some new generative devices are defined, called pattern grammars, starting from the way of identifying a language by a pattern in [2,5] (they can be viewed also as a generalization of Marcus contextual grammars [6]). The generative capacity of these grammars is investigated (compared mainly with L-language families), as well as closure, decision and descriptional complexity questions.

Semiconditional Contextual Grammars

One defines a class of contextual grammars “intermediate” between the conditional contextual grammars and the contextual grammars with bounded choice (the addition of each context depends on a prefix and a suffix of the current string which belong to a given pair of languages associated with this context). The paper investigates the generative capacity of these grammars compared to other contextual language families and with families in Chomsky hierarchy.

On some open problems about marcus contextual languages

The paper deals with four open problems in the monograph [8], namely it is proved here that: (i) there are inner contextual grammars generating matrix languages ofinfinite index (a half of problem P3 in [8]), (ii) the inner contextual grammars with bounded choice can generate non-context-free languages (PI8 in [8]), (iii) each regular-conditional contextual grammar generates a context-free language (P13 in [8]) and (iv) the relations between contextual languages and L-families (P4 in [8] are investigated

On contextual grammar forms

The grammatical families of all languages generated by simple contextual grammars which are obtained by (strict) interpretations of a simple contextual grammar are investigated. Their hierarchies and their closure properties with respect to the AFL-operations are studied.

Book Reviews

Books reviewed in this article:Balmuth, Miriam (1982) The Roots of Phonics: a historical introduction.Resnick, Daniel P. (1983) Literacy in Historical Perspective.Banfield, Ann (1982) Unspeakable Sentences: Narration and Representation in the Language of Fiction.Winter, Eugene (1982) Towards a Contextual Grammar of English: the Clause and Its Place in the Definition of Sentence.Hoey, Michael (1983) On the Surface of Discourse.Nuttall, C. (1982) Teaching Reading Skills in a Foreign Language.Berger, A. and Robinson, H.A. (Ed.) (1982) Secondary School Reading: What Research Reveals for Classroom Practice.Chapman, L.J. (1983) Reading Development and Cohesion.Engelkamp, J. and Zimmer, H.D. (1983) Dynamic Aspects of Language Processing.

Remarks on the Complexity of Regulated Rewriting

We compare the description of languages by context free, Indian parallel, Russian parallel, programmed, matrix, and random context grammars with respect to the number of nonterminals.

On grammar forms with terminal context

A context-free grammar form G defines a family of context-free grammars {ie397-01}(G). In this paper {ie397-02}(G) is extended to give the family of terminal context grammars {ie397-03}(G), which were introduced by Book [4]. It is shown that the families of languages defined by {ie397-04}(G) and {ie397-05}(G) are equal when G is an ?-free context-free grammar form. This generalizes the result of Book [4] for context-free grammars and underlines the usefulness of the notion of grammar forms in formal language theory.

Precedence analysis and context conditions

IT IS shown that every LR(k)-grammar is equivalent to some context grammar. An algorithm for the analysis of LR(k)-grammars connected with this interpretation is presented. The advisability of using context grammars for describing programming languages is considered. The concept of a precedence context grammar used for describing a programming language is defined. A syntactical analysis algorithm is presented which can be constructed from such a grammar automatically.

On the Parsing of Deterministic Languages

A parsing method for strict deterministic grammars is presented and a technique for using it to parse any deterministic language is indicated. An important characterization of the trees of strict deterministic grammars is established. This is used to prove iteration theorems for (strict) deterministic languages, and hence proving that certain sets are not in these families becomes comparatively straightforward. It is shown that every strict deterministic grammar is LR(0) and that any strict deterministic grammar is equivalent to a bounded right context (1, 0) grammar. Thus rigorous proofs that the families of deterministic, LR ( k ), and bounded right context languages are coextensive are presented for the first time.

Normal forms for context-sensitive grammars

In this paper, we mainly study the relation between scattered context grammars, which are an example for regulated context-free rewriting devices, and context-sensitive grammars. Emphasis is laid upon both normal form characterizations of context-sensitive grammars and an argument in how far scattered context grammars are stronger, with respect to generative capacity than unordered scattered context grammars.

Some restrictive devices for context-free grammars

For context-free grammars the restrictive devices of unordered scattered context, random context, partial ordering of productions and concatenation of productions in matrices are compared with respect to their generative power. This leads to two new characterizations of the family of type O languages in terms of unordered scattered context grammars and random context grammars, respectively. Languages generated by context-free grammars by imposing one of the above-mentioned restrictive devices or programming, regular control language, periodic time-variance or context-sensitivity are shown to have in the case of finite index a property similar to the “uvwxyproperty≓ of context-free languages.

A note on scattered context grammars

Abstract : Scattered context grammars can be regarded as web grammars in which the web is the transitive closure of string. It is an open question whether such grammars are strictly weaker than context-sensitive grammars. The report shows that if 'negative context' is allowed, they are as strong as context-sensitive grammars. Negative context alone appears to be comparable in power to (positive) scattered context, but it has not yet been shown that negative context grammars are strictly weaker than context-sensitive grammars. Unordered (positive or negative) scattered context is apparently even weaker, though still stronger than context-free; in web grammar terms, it corresponds to using the complete (undirected) web. (Author)

Scattered context grammars

Scattered context grammars are defined and the closure properties of the family of languages generated are considered. This family of languages is contained in the family of context sensitive languages and contains all languages accepted by linear time nondeterministic Turing machines.

On the placement of accent in dialogue: A feature of context grammar

It is well known that an English sentence may have its accent, or point of greatest prominence, on any of several syllables. This phenomenon has been called SHIFT.1 It is the feature of English that permits us to render such a sentence as The man can see the boy in a variety of ways, as follows:The man can see the Boy.The man can SEE the boy.The man CAN see the boy.The MAN can see the boy.

Bounded context syntactic analysis

Certain phase structure grammars define languages in which the phrasehood and structure of a substring of a sentence may be determined by consideration of only a bounded context of the substring. It is possible to determine, for any specified bound on the number of contextual characters considered, whether a given grammar is such a bounded context grammar . Such grammars are free from syntactic ambiguity. Syntactic analysis of sentences in a bounded context language may be performed by a standard process and requires a number of operations proportional to the length of sentence analyzed. Bounded context grammars form models for most languages used in computer programming, and many methods of syntactic analysis, including analysis by operator precedence, are special cases of bounded context analysis.