context-free grammar


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context-free grammar

[′kän‚tekst ‚frē ′gram·ər]
(computer science)
A grammar in which any occurrence of a metavariable may be replaced by one of its alternatives.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The defined process consists of building a lexicon, a context-free grammar and using the NLTK recursive-descent parser.
According to Proposition 29, [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], where (a, b) [member of] ([X.sup.[conjuction]]\{0}) x ([Y.sub.[disjunction]]\{1}, X = Im([[mu].sub.[rho]]), Y = Im([v.sub.[rho]]), 0 [less than or equal to] a + b [less than or equal to] 1 and the classical context-free grammar [G.sub.ab] = (N', T, P['.sub.ab], S') is shown in the proof process of of Proposition 29.
Let G' be a context-free grammar constructed from a regular tree grammar in normal form.
Proposition 2 Planar maps and several families of lattice paths (like Gessel walks) are not N-algebraic (i.e., they can not be generated by an unambiguous context-free grammar).
Roughly, a parser for a context-free grammar is a function that maps a sequence of terminals [Xi] to a derivation from the start symbol to [Xi].
Computation of the Probability of Initial Substring Generation by Stochastic Context-Free Grammars. Computational Linguistics 17:315-324.
The identifier that precedes the colon is the name used for a nonliteral basic symbol in the accompanying context-free grammar. Since comments do not appear in the grammar, no identifiers are given for them.
More formally, a supergraph path is said to be a same-level valid path if the sequence of labels on the call and return edges of the path belongs to the language of balanced parentheses generated from the nonterminal matched by the following context-free grammar:
By specifying translations on individual rules of a context-free grammar, we are able to gain much power with minimal annotations to the grammar.
"Although you can't deal with a language that has redoubling and duplication using a context-free grammar, and therefore there are certain parsing techniques, familiar in computer scient, that won't work on a language like that," he says, "nevertheless, you can easily devise another technique that will."

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