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In formal language theory, a context-free grammar is in Greibach normal form (GNF) if the right-hand sides of all production rules start with a terminal symbol, optionally followed by some variables. A non-strict form allows one exception to this format restriction for allowing the empty word (epsilon, ε) to be a member of the described language.
Translation of an English sentence to first-order logic. Logic translation is the process of representing a text in the formal language of a logical system.If the original text is formulated in ordinary language then the term natural language formalization is often used.
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.
Formal languages are used as tools in multiple disciplines. However, formal language theory rarely concerns itself with particular languages (except as examples), but is mainly concerned with the study of various types of formalisms to describe languages. For instance, a language can be given as those strings generated by some formal grammar;
Formal grammar; Formal language; Formal system; Generalized star height problem; Kleene algebra; Kleene star; L-attributed grammar; LR-attributed grammar; Myhill-Nerode theorem; Parsing expression grammar; Prefix grammar; Pumping lemma; Recursively enumerable language; Regular expression; Regular grammar; Regular language; S-attributed grammar ...
To convert a grammar to Chomsky normal form, a sequence of simple transformations is applied in a certain order; this is described in most textbooks on automata theory. [4]: 87–94 [5] [6] [7] The presentation here follows Hopcroft, Ullman (1979), but is adapted to use the transformation names from Lange, Leiß (2009).
The formalism of context-free grammars was developed in the mid-1950s by Noam Chomsky, [3] and also their classification as a special type of formal grammar (which he called phrase-structure grammars). [4] Some authors, however, reserve the term for more restricted grammars in the Chomsky hierarchy: context-sensitive grammars or context-free ...
Given that much work on English syntactic parsing depended on the Penn Treebank, which used a constituency formalism, many works on dependency parsing developed ways to deterministically convert the Penn formalism to a dependency syntax, in order to use it as training data. One of the major conversion algorithms was Penn2Malt, which ...