Natural Language Processing - Tutorialspoint

Natural Language Processing

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Natural Language Processing

About the Tutorial

Language is a method of communication with the help of which we can speak, read and

write. Natural Language Processing (NLP) is a subfield of Computer Science that deals with

Artificial Intelligence (AI), which enables computers to understand and process human

language.

Audience

This tutorial is designed to benefit graduates, postgraduates, and research students who

either have an interest in this subject or have this subject as a part of their curriculum.

The reader can be a beginner or an advanced learner.

Prerequisites

The reader must have basic knowledge about Artificial Intelligence. He/she should also be

aware about basic terminologies used in English grammar and Python programming

concepts.

Copyright & Disclaimer

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Natural Language Processing

Table of Contents

About the Tutorial ............................................................................................................................................ i

Audience ........................................................................................................................................................... i

Prerequisites ..................................................................................................................................................... i

Copyright & Disclaimer ..................................................................................................................................... i

Table of Contents ............................................................................................................................................ ii

1.

Natural Language Processing ¨C Introduction ............................................................................................. 1

History of NLP .................................................................................................................................................. 1

Study of Human Languages ............................................................................................................................. 2

Ambiguity and Uncertainty in Language ......................................................................................................... 3

NLP Phases....................................................................................................................................................... 5

2.

Natural Language Processing ¡ª Linguistic Resources ................................................................................ 7

Corpus ............................................................................................................................................................. 7

Elements of Corpus Design .............................................................................................................................. 7

TreeBank Corpus ............................................................................................................................................. 8

Types of TreeBank Corpus ............................................................................................................................... 9

Applications of TreeBank Corpus .................................................................................................................... 9

PropBank Corpus ............................................................................................................................................. 9

VerbNet(VN) .................................................................................................................................................. 10

WordNet ........................................................................................................................................................ 10

3.

Natural Language Processing ¡ª Word Level Analysis.............................................................................. 11

Regular Expressions ....................................................................................................................................... 11

Properties of Regular Expressions ................................................................................................................. 11

Examples of Regular Expressions .................................................................................................................. 12

Regular Sets & Their Properties..................................................................................................................... 12

Finite State Automata.................................................................................................................................... 13

Relation between Finite Automata, Regular Grammars and Regular Expressions ....................................... 13

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Types of Finite State Automation (FSA) ......................................................................................................... 14

Morphological Parsing ................................................................................................................................... 16

Types of Morphemes ..................................................................................................................................... 17

4.

Natural Language Processing ¡ª Syntactic Analysis ................................................................................. 19

Concept of Parser .......................................................................................................................................... 19

Types of Parsing ............................................................................................................................................. 19

Concept of Derivation.................................................................................................................................... 20

Types of Derivation........................................................................................................................................ 20

Concept of Parse Tree ................................................................................................................................... 20

Concept of Grammar ..................................................................................................................................... 20

Phrase Structure or Constituency Grammar ................................................................................................. 21

Dependency Grammar .................................................................................................................................. 22

Context Free Grammar .................................................................................................................................. 23

Definition of CFG ........................................................................................................................................... 24

5.

Natural Language Processing ¡ª Semantic Analysis ................................................................................. 25

Elements of Semantic Analysis ...................................................................................................................... 25

Difference between Polysemy and Homonymy ............................................................................................ 26

Meaning Representation ............................................................................................................................... 26

Approaches to Meaning Representations ..................................................................................................... 27

Need of Meaning Representations ................................................................................................................ 27

Lexical Semantics ........................................................................................................................................... 27

6.

Natural Language Processing ¡ª Word Sense Disambiguation ................................................................. 29

Evaluation of WSD ......................................................................................................................................... 29

Approaches and Methods to Word Sense Disambiguation (WSD) ............................................................... 30

Applications of Word Sense Disambiguation (WSD) ..................................................................................... 30

Difficulties in Word Sense Disambiguation (WSD) ........................................................................................ 31

7.

Natural Language Processing ¡ª Discourse Processing ............................................................................ 33

Concept of Coherence ................................................................................................................................... 33

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Discourse structure ....................................................................................................................................... 33

Algorithms for Discourse Segmentation ........................................................................................................ 33

Text Coherence.............................................................................................................................................. 34

Building Hierarchical Discourse Structure ..................................................................................................... 35

Reference Resolution .................................................................................................................................... 35

Terminology Used in Reference Resolution .................................................................................................. 36

Types of Referring Expressions ...................................................................................................................... 36

Reference Resolution Tasks ........................................................................................................................... 37

8.

Natural Language Processing ¡ª Part of Speech (PoS) Tagging ................................................................ 38

Rule-based POS Tagging ................................................................................................................................ 38

Properties of Rule-Based POS Tagging .......................................................................................................... 38

Stochastic POS Tagging .................................................................................................................................. 39

Properties of Stochastic POS Tagging ............................................................................................................ 39

Transformation-based Tagging ...................................................................................................................... 39

Working of Transformation Based Learning (TBL) ......................................................................................... 40

Advantages of Transformation-based Learning (TBL) ................................................................................... 40

Disadvantages of Transformation-based Learning (TBL) ............................................................................... 40

Hidden Markov Model (HMM) POS Tagging ................................................................................................. 40

Hidden Markov Model ................................................................................................................................... 40

Use of HMM for POS Tagging ........................................................................................................................ 42

9.

Natural Language Processing ¡ª Natural Language Inception .................................................................. 44

Natural Language Grammar .......................................................................................................................... 44

Components of Language .............................................................................................................................. 44

Grammatical Categories ................................................................................................................................ 45

Spoken Language Syntax ............................................................................................................................... 48

10. Natural Language Processing ¡ª Information Retrieval ........................................................................... 49

Classical Problem in Information Retrieval (IR) System................................................................................. 49

Aspects of Ad-hoc Retrieval ........................................................................................................................... 50

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