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Machine Translation
Dr. Nizar HabashResearch Scientist
Center for Computational Learning SystemsColumbia University
COMS E6998: Topics in Computer Science
Spring 2013
Session #1
• Introductions• Syllabus Explanation• Lecture
– Why Machine Translation– Multilingual Challenges for MT– MT Approaches– MT Evaluation
Why (Machine) Translation?
Languages in the world• 6,800 living languages• 600 with written tradition • 100 languages are spoken by 95% of world population
Translation Market• $26 Billion Global Market
(2010)• Doubling every five years
(Donald Barabé, invited talk, MT Summit 2003)
MultilingualismTower of Babel
• Genesis 11:1-91 And the whole earth was of one
language, and of one speech....9 Therefore is the name of it called
Babel; because the Lord did there confound the language of all the earth: and from thence did the Lord scatter them abroad upon the face of all the earth.
• Foremost symbol of multilingualism as a problem
MultilingualismRosetta Stone
• Ancient Egyptian stele (196 BCE )• Key to modern understanding of
Egyptian hieroglyphs• Trilingual document:
– ancient Egyptian hieroglyphs– Egyptian demotic script– ancient Greek
• Common symbol of parallel corpora and translation solutions
Multilingual Challenges
• nai you duo shi means buttered toast• naiyou means butter• duoshi means toast• duo means many • shi can mean private (as in the army rank)
Why (Machine) Translation?
Languages in the world• 6,800 living languages• 600 with written tradition • 100 languages are spoken by 95% of world population
Translation Market• $26 Billion Global Market
(2010)• Doubling every five years
(Donald Barabé, invited talk, MT Summit 2003)
Machine TranslationScience Fiction
• Star Trek Universal Translator an "extremely sophisticated computer
program" which functions by "analyzing the patterns" of an unknown foreign language, starting from a speech sample of two or more speakers in conversation. The more extensive the conversational sample, the more accurate and reliable is the "translation matrix"….
Machine TranslationScience Fiction
• Futurama Universal TranslatorDr. Farnsworth: “This is my
Universal Translator, although it only translate into an incomprehensible dead language”
Cubert: “Hello!” Machine: “Bonjour!”Dr. Farnsworth: "Imcomprehensible gibberish”
Machine TranslationScience Fiction
• The Babel FishThe Hitch Hiker's Guide to the Galaxy" (Douglas Adams)
"is small, yellow and leech-like, ... if you stick a Babel fish in your ear you can instantly understand anything said to you in any form of language…"
• Currently, Google offers translations between the following languages over 3,000 pairs
Afrikaans
Albanian
Arabic
Armenian
Azerbaijani
Basque
Belarusian
Bulgarian
Catalan
Chinese
Croatian
Czech
Danish
Dutch
English
Estonian
Filipino
Finnish
French
Galician
Georgian
German
Greek
Haitian Creole
Hebrew
Hindi
Hungarian
Icelandic
Indonesian
Irish
Italian
Japanese
Korean
Latvian
Lithuanian
Macedonian
Malay
Maltese
Norwegian
Polish
Portuguese
Romanian
Russian
Serbian
Slovak
Slovenian
Spanish
Swahili
Swedish
Thai
Turkish
Ukrainian
Urdu
Vietnamese
Welsh
Yiddish
Why Machine Translation?• Full Translation
– Domain specific, e.g., Weather reports
• Machine-aided Translation– Requires post-editing
• Cross-lingual NLP applications– Cross-language IR– Cross-language Summarization
• Testing grounds – Extrinsic evaluation of NLP tools, e.g., parsers, pos
taggers, tokenizers, etc.
Multilingual Challenges
• Orthographic Variations– Ambiguous spelling
• اشعارا االوالد ك�ت�ب� كتب اشع�ارا األو�الد�
– Ambiguous word boundaries•
• Lexical Ambiguity– Bank بنك (financial) vs. ضفة (river)– Eat essen (human) vs. fressen (animal)
Multilingual Challenges Morphological Variations
• Affixational (prefix/suffix) vs. Templatic (Root+Pattern)
write written كتب
بوكتم
kill killed قتل لوقتم
do done فعل لوفعم
conj
noun
pluralarticle
• Tokenization (aka segmentation+normalization)
And the cars and the cars
اتسيارالو w Al SyArAt
Et les voitures et le voitures
Morphology
• Arabic: very rich morphology: number, gender, case, person, aspect, voice, several clitics, etc.– Arabic tokenization
• English: simple morphology • Chinese: no morphology – quantifiers & verbal aspects
الصف كتاباالمجتهد الطالبيقرأ في الصين عنread the-student the-diligent a-book about china in the-classroom
the diligent student is reading a book about china in the classroom
这位勤奋的学生在教室读一本关于中国的书this quant diligent de student in classroom read one quant about china de book
Syntax
Arabic English ChineseSubj-Verb V Subj Subj V Subj V Subj … V
Verb-PP V…PP V…PP V PP PP V
Adjectives N Adj Adj N Adj de N
Possessives N Poss N of Poss Poss ’s N Poss de N
Relatives N Rel N Rel Rel de N
المجتهد يقرأ الصين الطالب عن الصف كتابا فيread the-student the-diligent a-book about china in the-classroom
the diligent student is reading a book about china in the classroom
这位勤奋的学生在教室读一本关于中国的书this quant diligent de student in classroom read one quant about china de book
Syntaxالصين كتابا المجتهد الطالبيقرأ الصف عن في
read the-student the-diligent a-book about china in the-classroom
the diligent student is reading a book about china in the classroom
这位勤奋的学生在教室读一本关于中国的书this quant diligent de student in classroom read one quant about china de book
Arabic English ChineseSubj-Verb V Subj Subj V Subj V Subj … V
Verb-PP V…PP V…PP V PP PP V
Adjectives N Adj Adj N Adj de N
Possessives N Poss N of Poss Poss ’s N Poss de N
Relatives N Rel N Rel Rel de N
هنا لستI-am-not here
am
I here
I am not here
not
تلس
هنا
Translation Divergencesconflation
Je ne suis pas iciI not am not here
suis
Je icine pas
*نا ا بردان
*קר ל
بردانانا I cold
be
I cold
I am cold ליקרcold for-me
אני
Translation Divergencescategorial, thematic and structural
tener
Yo frio
tengo frioI-have cold
swim
I quicklyacross
river
I swam across the river quickly
Translation Divergenceshead swap and categorial
اسرع
انا عبورسباحة
نهر
سباحة النهر عبور اسرعتI-sped crossing the-river swimming
swim
I quicklyacross
river
I swam across the river quickly
Translation Divergences head swap and categorial
חצה
אני אתב
נהר
ב
שחיה מהירות
חציתי את הנהר בשחיה במהירותI-crossed obj river in-swim speedily
Translation Divergences head swap and categorial
חצה
אני אתב
נהר
ב
שחיה מהירות
اسرع
انا عبورسباحة
نهر
swim
I quicklyacross
river
noun
prep
verb
noun
adverb
verb
nounverb
noun
Translation DivergencesOrthography+Morphology+Syntax
妈妈的车 mama de che
car
mom
possessed-by
mom’s car
ماما ةسيارsayyArat mama
la voiture de maman
Knowledge Acquisition Strategy
Knowledge Representation Strategy
All manual
Deep/ Complex
Shallow/ Simple
Fully automated
Learn from un-annotated data
Phrase tables
Word-based only
Learn from annotated data
Example-based MT
Original statistical MT
Typical transfer system
Classic interlingual system
Original direct approach
Syntactic Constituent Structure
Interlingua
New Research Goes Here!
Semantic analysis
Hand-built by non-experts
Hand-built by experts
Electronic dictionaries
MT Strategies (1954-2004)
Slide courtesy ofLaurie Gerber
MT ApproachesMT Pyramid
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation
Gisting
MT ApproachesGisting Example
Sobre la base de dichas experiencias se estableció en 1988 una metodología.
Envelope her basis out speak experiences them settle at 1988 one methodology.
On the basis of these experiences, a methodology was arrived at in 1988.
MT ApproachesMT Pyramid
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation
Gisting
Transfer
MT ApproachesTransfer Example
• Transfer Lexicon – Map SL structure to TL structure
poner
X mantequilla en
Y
:obj:mod:subj
:obj
butter
X Y
:subj :obj
X puso mantequilla en Y X buttered Y
MT ApproachesMT Pyramid
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation
Gisting
Transfer
Interlingua
MT ApproachesMT Pyramid
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation
Interlingua
Gisting
Transfer
MT ApproachesMT Pyramid
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation
Interlingual Lexicons
Dictionaries/Parallel Corpora
Transfer Lexicons
MT ApproachesMT Pyramid
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation
Interlingual Lexicons
Dictionaries/Parallel Corpora
Transfer Lexicons
MT ApproachesStatistical vs. Rule-based
Source word
Source syntax
Source meaning Target meaning
Target syntax
Target word
Analysis Generation