A computational analysis of nepali morphology. A model for natural language processing

380 Pages·3.795 MB·Nepali-English

by  Prasain Balaram.

A COMPUTATIONAL ANALYSIS OF NEPALI MORPHOLOGY:
A MODEL FOR NATURAL LANGUAGE PROCESSING

A Dissertation

Submitted to the Faculty of Humanities and Social Sciences of

Tribhuvan University in Fulfillment of the Requirements for the Degree
of

DOCTOR OF PHILOSOPHY

in

LINGUISTICS

By

BALARAM PRASAIN

Ph.D. Reg. No.: 19-2058 Magh
TU Reg. No.: 288-83

March 2011

ACKNOWLEDGEMENTS

My profound indebtedness is due to my supervisor prof. Dr. Yogendra Prasad
Yadava, the former head, Central Department of Linguistics, Tribhuvan University,
Nepal for his insistent encouragement, continuous guidance, valuable suggestions and
insightful comments in accomplishing this dissertation.
I would like to express my sincere gratitude to Professor Dr. Miriam Butt, Department
of Linguistics, Konstanz University, Germany for her constructive suggestions, proper
guidance, insightful comments to improve this dissertation.
I owe a great deal to Dr. Andrew Hardie, Lancaster University, for his valuable
suggestions and providing his articles which help me understand the basic concepts
and also for helping in using online NNC corpus.
I would like to extend my thanks to Dr. Dan Raj Regmi, head of the Central
Department of Linguistics, Tribhuvan University, for his encouragement, useful
suggestions and comments provided to my study.
I would like to extend my sincere gratitude to Prof. Madhav Prasad Pokharel, Central
Department of Linguistics, Tribhuvan University, for his prompt answer to any
queries regarding Nepali morphology and its structure.
I would like to express my gratitude to Prof. Dr. Chuda Mani Bandhu and Prof. Dr.
Tej R. Kansakar, Former heads, Central Department of Linguistics, for their
inspiration and encouragement given to this study.
I extend my thanks to Krishna Prasad Chalise, Central Department of Linguistics,
Dubi Nanda Dhakal, Central Department of Linguistics, Krishna Poudel, Central
Department of Linguistics, for their valuable comments and active participation in
discussion whenever the problem was raised.
I am equally thankful to Ram Raj Lohani, Central Department of Linguistics, Bhim
Narayan Regmi, Central Department of Linguistics, Karnakhar Khatiwada, Central
Department of Linguistics, Bhim Lal Gautam, Central Department of Linguistics,
Krishna Prasad Parajuli, Central Department of Linguistics for their support and
encouragement.
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I am extremely thankful to Santa Bahadur Basnet for his tokenizer and a number of
computational concepts.
I would like to thank Madan Puraskar Library and its staff for their help in different
point of time.
My sincere thanks go to Dr. Tika Ram Poudel, Tina Bögel, Sebastian Sulger,
Kanstanz Univeristy for their help.
I would like to thank Tribhuvan University for providing me study leave for two
years, SIL International for providing me travel grants while attending the workshops
and institute in University of California, Bangkok, Thailand and IIT Hyderabada,
India; Bhashasanchar project for supporting me financially while attending the
training on text-to-speech in Gotenberg University, Sweden; and Department of
Linguistics, University of Kanstanz for supporting me financially to attend the school
of computational and natural language processing in Konstanz University, Germany.
I would like to take this opportunity to express my sincere appreciation to my spouse
Mrs. Nirmala Prasain, son Aryan Prasain and daughter Sanskriti Prasain for their
tolerance.
Finally, I express my thanks to all the Central Department’s non-teaching staff for
their help whenever required.

BALARAM PRASAIN
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ABSTRACT

The main goal of this study is to present a computational analysis of morphology in
Nepali for developing a model for natural language processing by applying the finite
state approach. The morphological categories have been analyzed according to the
principle of Two-level morphology (Koskeniemmi 1983), and these categories have
been implemented using Xerox finite state tool (Beesley and Kartumnen 2003) to
create the morphological analyzer. A version of finite state automaton called finite
state transducer is used in this study which handles relation between two languages,
namely upper language and lower language. Upper language is equivalent to lexical
level and lower language is equivalent to surface level. The finite state transducer is
bidirectional, i.e., moving from surface level to lexical level is analysis and from
lexical level to surface level is generation.
This study is organized into eight chapters. Chapter 1 presents the general
morphological concepts, the objectives, methodology, the significance and limitations
of the study. Chapter 2 presents the theoretical framework that is adopted for the
study. Chapter 3 analyzes nouns, pronouns, adjectives, numerals and classifiers in
Nepali. Chapter 4 analyzes the verbs in Nepali from computational approach in the
first part and verbal inflections in the second part. Chapter 5 deals with indeclinable
words in Nepali. Chapter 6 analyzes the derivational process. Chapter 7 implements
the outcome of analysis in previous chapters into a finite state transducer using Xerox
Finite State Tool. Chapter 8 summarizes the findings of the study.
This study has identified fourteen groups of nouns, eight groups of pronouns, four
groups of adjectives, one group of cardinal numerals, two groups of ordinal numerals,
three groups of classifiers, ten groups of verbs, seven groups of adverbs, two groups
of conjunctions, three groups of postpositions, one group of particles and fifteen
groups of derivations in Nepali. The phonological rules for each group have also been
identified. The finite state transducer for each group with corresponding
morphological tags and phonological rules have been created; and all of them have
been put together into a single transducer which can be used as a morphological
analyzer for Nepali.

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TABLE OF CONTENTS

Recommendation Letter i
Approval Letter ii
Declaration iii
Acknowledgments iv
Abstract vi
List of tables xiii
List of figures xx
List of abbreviations xxv

Chapter 1: Introduction 1
1.1 Background 1
1.2 Statement of the problem 6
1.3 Objectives of the study 7
1.3 Literature review 7
1.5 Significance of the study 16
1.6 Research methodology 16
1.7 Limitations 17
1.8 Organization of the study 17

Chapter 2: Theoretical framework 19
2.0 Outline 19
2.1 Computational concept 19
2.2 Regular expression 20
2.3 Finite state technology 22
2.4 Regular language 23
2.5. Finite state machine 24
2.5.1 Finite state automata (FSA) 24
2.5.2 Finite state transducer (FST) 25
2.5.3 Some important operations on FSTs 26
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2.6 FST in computational morphology 30
2.7 Xerox finite state tool syntax (XFST) 31
2.7.1 LEXC grammar 33
2.7.2 XFST interface 38
2.8 Summary 41

Chapter 3: Nominal morphology 42
3.0 Outline 42
3.1 Nouns in Nepali 42
3.1.1 Characteristics of nouns in Nepali 43
3.2 Classification of nouns in Nepali 55
3.2.1 O-ending nouns 55
3.2.2 Non-o-ending nouns 60
3.3 Pronouns 69
3.3.1 Characteristics of pronouns in Nepali 69
3.3.2 Grouping of pronouns 71
3.4 Adjectives 91
3.4.1 Characteristics of adjectives in Nepali 91
3.4.2 Classification of adjectives 95
3.5 Numerals 100
3.5.1 Cardinal numbers 100
3.5.2 Ordinal number 101
3.5.2 Other numerals 105
3.6 Classifiers in Nepali 107
3.6.1 Numeral classifiers 107
3.6.2 Quasi classifiers 108
3.7 Summary 110

Chapter 4: Verbal morphology 111
4.0 Outline 111
4.1 Characteristics of verb in Nepali 111
viii
4.1.1 Significant verb stem finals 111
4.1.2 Transitivity 118
4.1.3 Syllabicity 120
4.1.4 Sound आ a 122
4.2 Morphological processes 122
4.2.1 Causativization/transitivization 122
4.2.2 Passivization 127
4.2.3 Negativization 129
4.3 Stem formation 130
4.4 Grouping of verb stems 131
4.4.1 Intransitive verb stems 131
4.4.2 Transitive verb stem 138
4.4.3 Irregular verb stems 144
4.4.4 Suppletive verb stems 145
4.5 Verbal inflections 147
4.5.1 Auxiliary verbs in Nepali 147
4.5.2 Tense 155
4.5.3 Aspects 163
4.5.4 Moods 173
4.5.5 Participial forms 179
4.6 Summary 187

Chapter 5: Adverbs, conjunctions, postpositions and particles 188
5.0 Outline 188
5.1 Adverbs in Nepali 188
5.1.1 Temporal adverbs 188
5.1.2 Spatial adverbs 189
5.1.3 Amount adverbs 190
5.1.4 Manner adverbs 191
5.1.5 Frequency adverbs 191
5.1.6 Reason adverbs 192
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