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An extended context-free grammar (or regular right part grammar) is one in which the right-hand side of the production rules is allowed to be a regular expression over the grammar's terminals and nonterminals. Extended context-free grammars describe exactly the context-free languages.
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.
b. Sue i saw Judy j and ___ i/*j ran. c. Sue i saw Judy j, and she i/j was frightened. d. Sue i saw Judy j and ___ i/*j was frightened. The omitted subject argument of the embedded clause must correspond to the subject (nominative) of the matrix-clause. If it corresponds to the object (accusative), the sentence is ungrammatical.
A formal grammar describes which strings from an alphabet of a formal language are valid according to the language's syntax. A grammar does not describe the meaning of the strings or what can be done with them in whatever context—only their form. A formal grammar is defined as a set of production rules for such strings in a formal language.
Chomsky (1959) introduced the Chomsky hierarchy, in which context-sensitive grammars occur as "type 1" grammars; general noncontracting grammars do not occur. [2]Chomsky (1963) calls a noncontracting grammar a "type 1 grammar", and a context-sensitive grammar a "type 2 grammar", and by presenting a conversion from the former into the latter, proves the two weakly equivalent.
A grammar that uses phrase structure rules is a type of phrase structure grammar. Phrase structure rules as they are commonly employed operate according to the constituency relation, and a grammar that employs phrase structure rules is therefore a constituency grammar ; as such, it stands in contrast to dependency grammars , which are based on ...
A right-regular grammar (also called right-linear grammar) is a formal grammar (N, Σ, P, S) in which all production rules in P are of one of the following forms: A → a; A → aB; A → ε; where A, B, S ∈ N are non-terminal symbols, a ∈ Σ is a terminal symbol, and ε denotes the empty string, i.e. the string of length 0. S is called the ...
[5]: 71 This analysis was developed in a 1962 grammar by Barbara M. H. Strang [5]: 73 and in 1972 by Randolph Quirk and colleagues. [5]: 74 In 1985, A Comprehensive Grammar of the English Language appears to have been the first work to explicitly conceive of determiner as a distinct lexical category. [5]: 74