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1997
In chapter 5 we use finite automata for text parsing. As noted, there are rather simple structures (e.g., nested comments) that cannot be parsed with finite automata. There is a more powerful formalism called context-free grammars that is often used when finite automata are not enough.
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In chapter 5 we use finite automata for text parsing. As noted, there are rather simple structures (e.g., nested comments) that cannot be parsed with finite automata. There is a more powerful formalism called context-free grammars that is often used when finite automata are not enough.
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1984
A context-free grammar is a collection of context-free phrase structure rules. Each such rule names a constituent type and specifies a possible expansion thereof. The standard notation is: $$ {\rm{lhs}}\,\, \to \,\,{\rm{rh}}{{\rm{s}}_{\rm{1}}}\,\,.\,\,.\,\,.\,\,{\rm{rh}}{{\rm{s}}_{\rm{n}}} $$ where lhs names the constituent, and rhs1 through ...
Lincoln Wallen, Alan Bundy
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A context-free grammar is a collection of context-free phrase structure rules. Each such rule names a constituent type and specifies a possible expansion thereof. The standard notation is: $$ {\rm{lhs}}\,\, \to \,\,{\rm{rh}}{{\rm{s}}_{\rm{1}}}\,\,.\,\,.\,\,.\,\,{\rm{rh}}{{\rm{s}}_{\rm{n}}} $$ where lhs names the constituent, and rhs1 through ...
Lincoln Wallen, Alan Bundy
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Context-Free Grammars and XML Languages
2006We study the decision properties of XML languages. It was known that given a context-free language included in the Dyck language with sufficiently many pairs of parentheses, it is undecidable whether or not it is an XML language. We improve on this result by showing that the problem remains undecidable when the language is written on a unique pair of ...
A. Bertoni, C. Choffrut, B. Palano
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Context-Free Grammars with Lookahead
2021We introduce context-free grammars with lookahead. The grammars are an extension of both context-free grammars and parsing expression grammars, hence we can handle the two grammars in a unified way. To accommodate lookahead, we use a language with lookahead, which is a set of string pairs. We considered the grammar as a system of equations and give the
Takayuki Miyazaki, Yasuhiko Minamide
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Acta Informatica, 1994
A text is a tripleτ=(λ,ρ1,ρ2) such that λ is a labeling function, andρ1 andρ2 are linear orders on the domain of λ; hence τ may be seen as a word (λ,ρ1) together with an additional linear orderρ2 on the domain of λ. The orderρ2 is used to give to the word (λ,ρ1) itsindividual hierarchical representation (syntactic structure) which may be a tree but it ...
P. ten Pas +2 more
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A text is a tripleτ=(λ,ρ1,ρ2) such that λ is a labeling function, andρ1 andρ2 are linear orders on the domain of λ; hence τ may be seen as a word (λ,ρ1) together with an additional linear orderρ2 on the domain of λ. The orderρ2 is used to give to the word (λ,ρ1) itsindividual hierarchical representation (syntactic structure) which may be a tree but it ...
P. ten Pas +2 more
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1993
Context-free grammars are a language for defining languages. Not all languages can be defined by a context-free grammar — only the (yes) context-free ones. Suppose we want to define the language of a small child, who continually says sentences like “want cookie”. His or her sentences consist of a verb followed by a noun.
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Context-free grammars are a language for defining languages. Not all languages can be defined by a context-free grammar — only the (yes) context-free ones. Suppose we want to define the language of a small child, who continually says sentences like “want cookie”. His or her sentences consist of a verb followed by a noun.
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Indexed Grammars—An Extension of Context-Free Grammars
Journal of the ACM, 1967A new type of grammar for generating formal languages, called an indexed grammar, is presented. An indexed grammar is an extension of a context-free grammar, and the class of languages generated by indexed grammars has closure properties and decidability results similar to those for context-free languages.
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A REGULARITY CONDITION FOR CONTEXT-FREE GRAMMARS
International Journal of Foundations of Computer Science, 2008We define a complexity measure on context-free grammars called end. Roughly speaking, for a context-free grammar G, endG(n) measures the distance of variables from the ends of sentential forms along the derivations of words in L(G) of length n. We prove in a constructive way the regularity of L(G)wheneverendG(n)is constant.
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Context-Free Grammars and Languages
1977You may have seen something like the following used to give a formal defini-tion of a language. This notation is sometimes called BNF for Backus-Naur form.
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Context-free grammars on trees
Proceedings of the first annual ACM symposium on Theory of computing - STOC '69, 1969In this paper we discuss still another version of indexed grammars 1 and macro grammars3,gaining some geometric intuition about the structure of these systems. An ordinary context-free grammar is a rewriting system for strings; we find that a macro grammar is a rewriting system for trees.
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