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Context free

Grammar

By :

KalpanaNagle



Points to be discussed

•

• What is grammar.

• Who developed the context free grammar.

• More focused on context free grammar.•

• Relation with artificial intelligent.•

• Importance of context free grammar .



What is Grammar

•

• Grammar is the study of rules governing the use of language.

• The set of rules governing aparticular language is alsocalled the grammar of the

language; thus, eachlanguage can be said tohave its own distinctgrammar.

•

• Grammar is art of the



… What is Grammar

Definition : A Grammar G is defined as an orderedquadruple of the form

•

• G = ( V N , V T , S, P )•

• where the entries are identified as follows: V N is anonterminal consisting of the lexical and syntacticcategory labels;

•

•

V T denotes a set of words, called the terminal of G; •

• S is a special member of V N that, in addition to beingthe label of the sentence category, identifies thestarting symbol of G; and

•



oam Chomskoam Chomsk

oam Chomsky lassified the

rammar into 4.ategories



Chomsky classification ofGrammar

Type Name Type of Productions

0 Unrestricted

1 Context-Sensitive

2 Context-Free

3 Regular, Finite



C ntext Free Grammar ntext Free Grammar

A ormal grammar ,is a precisely defined grammar typically used for o mp ut er p ro gr am mi ng

languages .

A en er at ive grammar is a ormal grammar that" " -can in some sense generate the well formed

expressions of a .atural language

An entire branch of in gu ist ic theory is based on.generative grammars e ne ra ti ve g ram ma rs were

popularized by .oam Chomsky



C ntext Free Grammar ntext Free Grammar

-Context free grammars play a central role in the description and design f r og ra mmi ng la ng ua ge s

and .ompilers

They are also used for analyzing the syntax of.a tural languag es

oam Chomsky has posited that all uman anguages are based on ontext free grammars



atural language atural languageprocessingrocessing

atural language( )rocessing NLP is the use

of computers to understand uman languages .

enerat ive g ra mma r is the use of rules to onstruct

.entences

oam Chomsky has posited that all uman languages are based on ontext free

grammars




( )The goal of Natural Language Processing NLP is to,design and build a computer system that will analyze

, - .understand and generate natural human languages

Applications of NLP include machine translation of- ;one human language text to another

- ,Generation of human language text such as fiction, ;manuals and general descriptions interfacing to other systems such as databases and robotic systems

-Thus enabling the use of human language type commands; -and queries and understanding human language text to

.provide a summary or to draw conclusions




One of the easiest tasks for a NLP system is to parse.a sentence to determine its syntax

A more difficult task is determining the semantic.meaning of a sentence One of the most difficult tasks

is the analysis of the context to determine the true.meaning and comparing that with other text



Computers

r ti fi ci a l Int el ligence Algorithms

Databases

Networking

Robotics

Search

at ural L anguage P roces sing

InformationRetrieval

achineTranslation

anguageAnalysis

Semantics Parsing



Natural Language Processing

•

• Subfield of Artificial Intelligence (AI) – Typically seen as one part of knowledge

representation•

• Can also be seen as a combination of computer science and linguistics.

– Computational Linguistics•

• Applications – English as a command language – Database queries – Translation systems – Speech recognition systems



Linguistics

•

• Human language divides into five levels

1.2. Phonology• How sounds are used in language

3.4. Morphology

• Word formation

5.6. Syntax

• Sentence formation7.8. Semantics

•

Sentence meaning9.



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