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2. Context-free grammar - Wikipedia

   en.wikipedia.org/wiki/Context-free_grammar

   In formal language theory, a context-free grammar ( CFG) is a formal grammar whose production rules can be applied to a nonterminal symbol regardless of its context. In particular, in a context-free grammar, each production rule is of the form. with a single nonterminal symbol, and a string of terminals and/or nonterminals ( can be empty).

3. Chomsky hierarchy - Wikipedia

   en.wikipedia.org/wiki/Chomsky_hierarchy

   The general idea of a hierarchy of grammars was first described by Noam Chomsky in "Three models for the description of language". [1] Marcel-Paul Schützenberger also played a role in the development of the theory of formal languages; the paper "The algebraic theory of context free languages" [2] describes the modern hierarchy, including context-free grammars.

4. Context-free language - Wikipedia

   en.wikipedia.org/wiki/Context-free_language

   The set of all context-free languages is identical to the set of languages accepted by pushdown automata, which makes these languages amenable to parsing.Further, for a given CFG, there is a direct way to produce a pushdown automaton for the grammar (and thereby the corresponding language), though going the other way (producing a grammar given an automaton) is not as direct.

5. Context-sensitive grammar - Wikipedia

   en.wikipedia.org/wiki/Context-sensitive_grammar

   A context-sensitive grammar ( CSG) is a formal grammar in which the left-hand sides and right-hand sides of any production rules may be surrounded by a context of terminal and nonterminal symbols. Context-sensitive grammars are more general than context-free grammars, in the sense that there are languages that can be described by a CSG but not ...

6. Syntax diagram - Wikipedia

   en.wikipedia.org/wiki/Syntax_diagram

   Syntax diagrams (or railroad diagrams) are a way to represent a context-free grammar. They represent a graphical alternative to Backus–Naur form, EBNF, Augmented Backus–Naur form, and other text-based grammars as metalanguages. Early books using syntax diagrams include the "Pascal User Manual" written by Niklaus Wirth [1] (diagrams start at ...

7. Chomsky normal form - Wikipedia

   en.wikipedia.org/wiki/Chomsky_normal_form

   In formal language theory, a context-free grammar, G, is said to be in Chomsky normal form (first described by Noam Chomsky) [ 1] if all of its production rules are of the form: [ 2][ 3] A → BC, or. A → a, or. S → ε,

8. Backus–Naur form - Wikipedia

   en.wikipedia.org/wiki/Backus–Naur_form

   Backus–Naur form. In computer science, Backus–Naur form ( / ˌbækəs ˈnaʊər /) (BNF or Backus normal form) is a notation used to describe the syntax of programming languages or other formal languages. It was developed by John Backus and Peter Naur. BNF can be described as a metasyntax notation for context-free grammars.

9. Probabilistic context-free grammar - Wikipedia

   en.wikipedia.org/wiki/Probabilistic_context-free...

   Probabilistic context-free grammar. Grammar theory to model symbol strings originated from work in computational linguistics aiming to understand the structure of natural languages. [1] [2] [3] Probabilistic context free grammars ( PCFGs) have been applied in probabilistic modeling of RNA structures almost 40 years after they were introduced in ...