scholarly journals Tractable Lexical-Functional Grammar

2020 ◽  
Vol 46 (3) ◽  
pp. 515-569
Author(s):  
Jürgen Wedekind ◽  
Ronald M. Kaplan
Keyword(s):  
Natural Language ◽  
Large Scale ◽  
Expressive Power ◽  
Functional Grammar ◽  
Natural Languages ◽  
Worst Case ◽  
Lexical Functional Grammar ◽  
Rewriting Systems ◽  
Mathematical Properties ◽  
Context Free

The formalism for Lexical-Functional Grammar (LFG) was introduced in the 1980s as one of the first constraint-based grammatical formalisms for natural language. It has led to substantial contributions to the linguistic literature and to the construction of large-scale descriptions of particular languages. Investigations of its mathematical properties have shown that, without further restrictions, the recognition, emptiness, and generation problems are undecidable, and that they are intractable in the worst case even with commonly applied restrictions. However, grammars of real languages appear not to invoke the full expressive power of the formalism, as indicated by the fact that algorithms and implementations for recognition and generation have been developed that run—even for broad-coverage grammars—in typically polynomial time. This article formalizes some restrictions on the notation and its interpretation that are compatible with conventions and principles that have been implicit or informally stated in linguistic theory. We show that LFG grammars that respect these restrictions, while still suitable for the description of natural languages, are equivalent to linear context-free rewriting systems and allow for tractable computation.

Review Lecture - The algorithmic description of natural language

1972 ◽  
Vol 182 (1068) ◽  
pp. 255-276 ◽  
Keyword(s):  
Natural Language ◽  
Expressive Power ◽  
Scientific Study ◽  
Human Language ◽  
Human Beings ◽  
Natural Languages ◽  
Computer Languages ◽  
Computing Science ◽  
Almost All ◽  
Semantic Aspect

Human language is a uniquely rewarding subject of psychological investigation because of the richness of its structure and its wide expressive power; and the ability to communicate in language is a skill which is possessed by almost all adult human beings. But the scientific study of language calls for appropriate modes of description; and the concept of an algorithm enables one to relate the phenomena of language to those of behaviour in general. A useful paradigm is to be found in computing science, where algorithms are expressed as programs written in specially designed languages. Like computer languages, natural languages have both a syntactic and a semantic aspect; and human utterances can be viewed as programs to be implemented by the hearer. This idea has been used for the development of computer programs with which one can converse in simple English.

scholarly journals French de and en as expressions of the genitive case: a unified analysis within LFG and computational implementation in XLE

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Leonel Figueiredo de Alencar ◽  
Christoph Schwarze
Keyword(s):  
Natural Language ◽  
Deep Structure ◽  
Functional Grammar ◽  
Lexical Functional Grammar ◽  
Heterogeneous Structures ◽  
Wide Range ◽  
Computational Implementation ◽  
Systematic Relationships ◽  
Transformational Framework ◽  
Genitive Case

ABSTRACT The French clitic pro-form en represents a wide range of heterogeneous constituents: de-PP complements and adjuncts, partitive objects, and prepositionless objects of cardinals. The main goal of this paper is to formalize this relationship computationally in terms of genitive case. This is apparently the first non-transformational counterpart to Kayne (1975)’s unified analysis, which derives en from a deep structure with de by means of syntactic transformations. Transformational grammars are problematic from the parsing perspective. In order to test our analysis automatically on a large amount of data, we implemented it in a computational grammar of French in the Lexical-Functional Grammar (LFG) formalism using the XLE system. This non-transformational framework is particularly fit for expressing systematic relationships between heterogeneous structures and has successfully been used for the implementation of natural language grammars since the 1980s. We tested the implementation on 320 grammatical sentences and on an equal number of ungrammatical examples. It analyzed all grammatical examples and blocked almost 95% of the ungrammatical ones, showing a high empirical adequacy of the grammar.

Potential Structures for Conversations in Various Contexts

2020 ◽  
Author(s):  
Tony Seimon ◽  
Janeth Robinson
Keyword(s):  
Natural Language ◽  
Computational Linguistics ◽  
Language Processing ◽  
Applied Linguistics ◽  
Processing Parameter ◽  
Language Understanding ◽  
Natural Languages ◽  
Linguistic Model ◽  
Language Studies ◽  
Context Free

Computational Linguistics and Artificial Intelligence are increasingly demanding more effective contributions from language studies to Natural Language Processing. This fact has driven Applied Linguistics to produce knowledge to offer reliable models of linguistic production, which are not based only on formal rules of context-free grammars; but, in another way, take the natural language understanding as processing parameter. In a complementary way, there has been an increase in the scope of Applied Linguistics, the need to implement the processing of natural languages in the interaction between human and computer, incorporating the machine into its research and application practices. Among these demands, the search for models that extrapolate the order of prayer stands out, in particular by turning to the structure of texts and, consequently, to textual genres. Situating in this context, this article aims to contribute with solutions to the demands in relation to the study of conversational structures. Thus, it aims to offer a linguistic model of the grammatical systems that perform the potential structures for the conversations in various contexts. More specifically, it produces a model capable of describing the way in which the system networks are made and, consequently, how this dynamic explains the organization of the conversations.

scholarly journals LFG Generation by Grammar Specialization

2012 ◽  
Vol 38 (4) ◽  
pp. 867-915 ◽  
Author(s):  
Jürgen Wedekind ◽  
Ronald M. Kaplan
Keyword(s):  
Free Generator ◽  
Compact Representation ◽  
Mathematical Framework ◽  
Functional Grammar ◽  
Context Free Grammar ◽  
Lexical Functional Grammar ◽  
The Individual ◽  
The Given ◽  
Context Free ◽  
Free Language

This article describes an approach to Lexical-Functional Grammar (LFG) generation that is based on the fact that the set of strings that an LFG grammar relates to a particular acyclic f-structure is a context-free language. We present an algorithm that produces for an arbitrary LFG grammar and an arbitrary acyclic input f-structure a context-free grammar describing exactly the set of strings that the given LFG grammar associates with that f-structure. The individual sentences are then available through a standard context-free generator operating on that grammar. The context-free grammar is constructed by specializing the context-free backbone of the LFG grammar for the given f-structure and serves as a compact representation of all generation results that the LFG grammar assigns to the input. This approach extends to other grammatical formalisms with explicit context-free backbones, such as PATR, and also to formalisms that permit a context-free skeleton to be extracted from richer specifications. It provides a general mathematical framework for understanding and improving the operation of a family of chart-based generation algorithms.

scholarly journals Syntactic discontinuities in Latin – A treebank-based study

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Dag Haug
Keyword(s):  
Functional Grammar ◽  
Natural Languages ◽  
Frequency Distributions ◽  
Lexical Functional Grammar ◽  
Context Sensitive ◽  
Categorial Grammars ◽  
Tree Adjoining Grammars ◽  
Complex Patterns ◽  
Grammar Formalisms

Syntactic discontinuities are very frequent in classical Latin and yet this data was never considered in debates on how expressive grammar formalisms need to be to capture natural languages. In this paper I show with treebank data that Latin frequently displays syntactic discontinuities that cannot be captured in standard mildly context-sensitive frameworks such as Tree-Adjoining Grammars or Combinatory Categorial Grammars. I then argue that there is no principled bound on Latin discontinuities but that they display a broadly Zipfian distribution where frequency drops quickly for the more complex patterns. Lexical-Functional Grammar can capture these  discontinuities in a way that closely reflects their complexity and frequency distributions.

Probabilistic grammars and hierarchical Dirichlet processes

2018 ◽  
Author(s):  
Percy Liang ◽  
Michael Jordan ◽  
Dan Klein
Keyword(s):  
Natural Language ◽  
Language Processing ◽  
Dirichlet Process ◽  
Large Scale ◽  
Syntactic Structure ◽  
Model Fitting ◽  
Hierarchical Dirichlet Process ◽  
Object Of Study ◽  
Context Free ◽  
Probabilistic Context

This article focuses on the use of probabilistic context-free grammars (PCFGs) in natural language processing involving a large-scale natural language parsing task. It describes detailed, highly-structured Bayesian modelling in which model dimension and complexity responds naturally to observed data. The framework, termed hierarchical Dirichlet process probabilistic context-free grammar (HDP-PCFG), involves structured hierarchical Dirichlet process modelling and customized model fitting via variational methods to address the problem of syntactic parsing and the underlying problems of grammar induction and grammar refinement. The central object of study is the parse tree, which can be used to describe a substantial amount of the syntactic structure and relational semantics of natural language sentences. The article first provides an overview of the formal probabilistic specification of the HDP-PCFG, algorithms for posterior inference under the HDP-PCFG, and experiments on grammar learning run on the Wall Street Journal portion of the Penn Treebank.

scholarly journals Definition of Natural Languages Using Context-free Grammer: In Context of Dari Language

2019 ◽  
Vol 4 (2) ◽  
pp. 167-170
Author(s):  
Mahmood Asgharzada
Keyword(s):  
Natural Language ◽  
Formal Language ◽  
Formal Languages ◽  
Natural Languages ◽  
Computer Scientists ◽  
The Common ◽  
To Come ◽  
Definition Of ◽  
Context Free ◽  
Free Language

Formal definition of a natural language lets computers understand it; the languages have challenging complexity to come under representation of any formal language. Modeling assumptions, using formal languages, we can approximate the languages; and better approximation we do, more complexities of formal languages are resolved. Objective is to study current researches and possibilities to model Dari as a context-free language. Researchers have worked for more than 6 decades on definition of syntax of natural languages using context-free grammer. It is crucial that computer scientists to be able to thoroughly understand about which category of formal languages the natural language exist in in. In overall, our skill to decide the grammar type of natural languages performs a significant role in our capability to parse it. This review article concludes that discussed issue of the context-freeness of a certain language is regularly reliant on upon the level of complexity of the language. The common of languages investigated in this regard are languages of European family and Indo-Aryan languages liker Dari, Arabic and Pashto have not been adequately fortunate to be devoted thorough researches in this regard.

Linguistic Data Model for Natural Languages and Artificial Intelligence. Part 5. Introduction to Logic

Discourse ◽  
2020 ◽  
Vol 6 (3) ◽  
pp. 109-117
Author(s):  
O. M. Polyakov
Keyword(s):  
Artificial Intelligence ◽  
Mathematical Logic ◽  
Natural Language ◽  
Semantic Interpretation ◽  
General View ◽  
World Model ◽  
Semantic Approach ◽  
Natural Languages ◽  
The World ◽  
Linguistic Aspect

Introduction. The article continues the series of publications on the linguistics of relations (hereinafter R–linguistics) and is devoted to an introduction to the logic of natural language in relation to the approach considered in the series. The problem of natural language logic still remains relevant, since this logic differs significantly from traditional mathematical logic. Moreover, with the appearance of artificial intelligence systems, the importance of this problem only increases. The article analyzes logical problems that prevent the application of classical logic methods to natural languages. This is possible because R-linguistics forms the semantics of a language in the form of world model structures in which language sentences are interpreted.Methodology and sources. The results obtained in the previous parts of the series are used as research tools. To develop the necessary mathematical representations in the field of logic and semantics, the formulated concept of the interpretation operator is used.Results and discussion. The problems that arise when studying the logic of natural language in the framework of R–linguistics are analyzed. These issues are discussed in three aspects: the logical aspect itself; the linguistic aspect; the aspect of correlation with reality. A very General approach to language semantics is considered and semantic axioms of the language are formulated. The problems of the language and its logic related to the most General view of semantics are shown.Conclusion. It is shown that the application of mathematical logic, regardless of its type, to the study of natural language logic faces significant problems. This is a consequence of the inconsistency of existing approaches with the world model. But it is the coherence with the world model that allows us to build a new logical approach. Matching with the model means a semantic approach to logic. Even the most General view of semantics allows to formulate important results about the properties of languages that lack meaning. The simplest examples of semantic interpretation of traditional logic demonstrate its semantic problems (primarily related to negation).

Sign in / Sign up

Export Citation Format

Share Document