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Range Concatenation Grammar
Range concatenation grammar (RCG) is a grammar formalism developed by Pierre Boullier in 1998 as an attempt to characterize a number of phenomena of natural language, such as Chinese numbers and German word order scrambling, which are outside the bounds of the mildly context-sensitive languages. From a theoretical point of view, any language that can be parsed in polynomial time belongs to the subset of RCG called positive range concatenation grammars, and reciprocally. Though intended as a variant on Groenink's literal movement grammars (LMGs), RCGs treat the grammatical process more as a proof than as a production. Whereas LMGs produce a terminal string from a start predicate, RCGs aim to reduce a start predicate (which predicates of a terminal string) to the empty string, which constitutes a proof of the terminal strings membership in the language. Description Formal definition A ''Positive Range Concatenation Grammar'' (PRCG) is a tuple G = (N,~T,~V,~S,~P), where: * N, T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scrambling (linguistics)
Scrambling is a syntax, syntactic phenomenon wherein sentences can be formulated using a variety of different word orders without a substantial change in meaning. Instead the reordering of words, from their canonical position, has consequences on their contribution to the discourse (i.e., the information's "newness" to the conversation). Scrambling does not occur in English language, English, but it is frequent in languages with freer word order, such as German language, German, Russian language, Russian, Persian language, Persian and Turkic languages. The term was coined by John R. Ross, John R. "Haj" Ross in his 1967 dissertation and is widely used in present work, particularly with the generative linguistics, generative tradition. Analysis Discourse Although scrambling does not change the semantic interpretation ("meaning") of the sentence, its scrambled configurations will be given in particular contexts related to discourse. This is the underlying information that cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mildly Context-sensitive Language
In computational linguistics, the term mildly context-sensitive grammar formalisms refers to several grammar formalisms that have been developed in an effort to provide adequate descriptions of the syntactic structure of natural language. Every mildly context-sensitive grammar formalism defines a class of mildly context-sensitive grammars (the grammars that can be specified in the formalism), and therefore also a class of mildly context-sensitive languages (the formal languages generated by the grammars). Background By 1985, several researchers in descriptive and mathematical linguistics had provided evidence against the hypothesis that the syntactic structure of natural language can be adequately described by context-free grammars.Riny Huybregts. "The Weak Inadequacy of Context-Free Phrase Structure Grammars". In Ger de Haan, Mieke Trommelen, and Wim Zonneveld, editors, ''Van periferie naar kern'', pages 81–99. Foris, Dordrecht, The Netherlands, 1984.Stuart M. Shieber.Evide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PTIME
In computational complexity theory, P, also known as PTIME or DTIME(''n''O(1)), is a fundamental complexity class. It contains all decision problems that can be solved by a deterministic Turing machine using a polynomial amount of computation time, or polynomial time. Cobham's thesis holds that P is the class of computational problems that are "efficiently solvable" or " tractable". This is inexact: in practice, some problems not known to be in P have practical solutions, and some that are in P do not, but this is a useful rule of thumb. Definition A language ''L'' is in P if and only if there exists a deterministic Turing machine ''M'', such that * ''M'' runs for polynomial time on all inputs * For all ''x'' in ''L'', ''M'' outputs 1 * For all ''x'' not in ''L'', ''M'' outputs 0 P can also be viewed as a uniform family of Boolean circuits. A language ''L'' is in P if and only if there exists a polynomial-time uniform family of Boolean circuits \, such that * For all n \in \m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Literal Movement Grammar
In linguistics and theoretical computer science, literal movement grammars (LMGs) are a grammar formalism intended to characterize certain extraposition phenomena of natural language such as topicalization and cross-serial dependency. LMGs extend the class of context free grammars (CFGs) by adding introducing pattern-matched function-like rewrite semantics, as well as the operations of variable binding and slash deletion. LMGs were introduced by A.V. Groenink in 1995.Groenink, Annius V. 1995. Literal Movement Grammars. In ''Proceedings of the 7th EACL Conference''. Description The basic rewrite operation of an LMG is very similar to that of a CFG, with the addition of arguments to the non-terminal symbols. Where a context-free rewrite rule obeys the general schema S \to \alpha for some non-terminal S and some string of terminals and/or non-terminals \alpha, an LMG rewrite rule obeys the general schema X(x_1, ..., x_n) \to \alpha, where X is a non-terminal with arity n (called a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 : A\ \to\ \alpha with A a ''single'' nonterminal symbol, and \alpha a string of terminals and/or nonterminals (\alpha can be empty). Regardless of which symbols surround it, the single nonterminal A on the left hand side can always be replaced by \alpha on the right hand side. This distinguishes it from a context-sensitive grammar, which can have production rules in the form \alpha A \beta \rightarrow \alpha \gamma \beta with A a nonterminal symbol and \alpha, \beta, and \gamma strings of terminal and/or nonterminal symbols. A formal grammar is essentially a set of production rules that describe all possible strings in a given formal language. Production rules are simple replacements. For example, the first rule in the picture, : \lan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undecidable Problem
In computability theory and computational complexity theory, an undecidable problem is a decision problem for which it is proved to be impossible to construct an algorithm that always leads to a correct yes-or-no answer. The halting problem is an example: it can be proven that there is no algorithm that correctly determines whether an arbitrary program eventually halts when run. Background A decision problem is a question which, for every input in some infinite set of inputs, requires a "yes" or "no" answer. Those inputs can be numbers (for example, the decision problem "is the input a prime number?") or values of some other kind, such as strings of a formal language. The formal representation of a decision problem is a subset of the natural numbers. For decision problems on natural numbers, the set consists of those numbers that the decision problem answers "yes" to. For example, the decision problem "is the input even?" is formalized as the set of even numbers. A decision pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formal Languages
In logic, mathematics, computer science, and linguistics, a formal language is a set of string (computer science), strings whose symbols are taken from a set called "#Definition, alphabet". The alphabet of a formal language consists of symbols that concatenate into strings (also called "words"). Words that belong to a particular formal language are sometimes called Formal language#Definition, ''well-formed words''. A formal language is often defined by means of a formal grammar such as a regular grammar or context-free grammar. In computer science, formal languages are used, among others, as the basis for defining the grammar of programming languages and formalized versions of subsets of natural languages, in which the words of the language represent concepts that are associated with meanings or semantics. In computational complexity theory, decision problems are typically defined as formal languages, and complexity classes are defined as the sets of the formal languages that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
