Harnessing the Power of Natural Language Processing (NLP ...
Introduction to NLP ch1 What is Natural Language Processing?
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Transcript of Introduction to NLP ch1 What is Natural Language Processing?
Dan Jurafsky
2
The original slides from:
http://web.stanford.edu/~jurafsky/NLPCourseraSlides.html
Some changes has done to these slides to fit with our NLP course
Dan Jurafsky
3
Natural language processing (NLP)is a field of computer science, artificial intelligence, and computational linguistics concerned with the interactions between computers and human (natural) languages
Major applications and tasks in NLP:• Machine translation• Named entity recognition• Part-of-speech tagging• Parsing• Question answering• Sentiment analysis• Speech recognition• Information retrieval• Information extraction• Automatic summarization
Dan Jurafsky
6
Information Extraction
Subject: curriculum meeting Date: January 15, 2012
To: Dan Jurafsky
Hi Dan, we’ve now scheduled the curriculum meeting.It will be in Gates 159 tomorrow from 10:00-11:30.-Chris Create new Calendar entry
Event: Curriculum mtgDate: Jan-16-2012Start: 10:00amEnd: 11:30amWhere: Gates 159
Dan Jurafsky
Information Extraction & Sentiment Analysis
• nice and compact to carry! • since the camera is small and light, I won't need to carry
around those heavy, bulky professional cameras either! • the camera feels flimsy, is plastic and very light in weight you
have to be very delicate in the handling of this camera7
Size and weight
Attributes: zoom affordability size and weight flash ease of use
✓
✗
✓
Dan Jurafsky
Information Extraction & Sentiment Analysis
• nice and compact to carry! • since the camera is small and light, I won't need to carry
around those heavy, bulky professional cameras either! • the camera feels flimsy, is plastic and very light in weight you
have to be very delicate in the handling of this camera8
Size and weight
Attributes: zoom affordability size and weight flash ease of use
✓
✗
✓
Dan Jurafsky
9
Machine Translation
• Fully automatic• Helping human translators
Enter Source Text:
Translation from Stanford’s Phrasal:
这 不过 是 一 个 时间 的 问题 .
This is only a matter of time.
Dan Jurafsky
Language Technology
Coreference resolution
Question answering (QA)
Part-of-speech (POS) tagging
Word sense disambiguation (WSD)Paraphrase
Named entity recognition (NER)
ParsingSummarization
Information extraction (IE)
Machine translation (MT)Dialog
Sentiment analysis
mostly solved
making good progress
still really hard
Spam detectionLet’s go to Agra!
Buy V1AGRA …
✓✗
Colorless green ideas sleep furiously. ADJ ADJ NOUN VERB ADV
Einstein met with UN officials in PrincetonPERSON ORG LOC
You’re invited to our dinner party, Friday May 27 at 8:30
PartyMay 27add
Best roast chicken in San Francisco!
The waiter ignored us for 20 minutes.
Carter told Mubarak he shouldn’t run again.
I need new batteries for my mouse.
The 13th Shanghai International Film Festival…
第 13届上海国际电影节开幕…
The Dow Jones is up
Housing prices rose
Economy is good
Q. How effective is ibuprofen in reducing fever in patients with acute febrile illness?
I can see Alcatraz from the window!
XYZ acquired ABC yesterdayABC has been taken over by XYZ
Where is Citizen Kane playing in SF?
Castro Theatre at 7:30. Do you want a ticket?
The S&P500 jumped
Dan Jurafsky
Ambiguity makes NLP hard:We say some input is ambiguousif there are multiple alternative linguistic structures than can be built for it.
Examples of the ambiguity :-Violinist Linked to JAL Crash Blossoms
Violinist Linked to JAL Crash BlossomsViolinist Linked to JAL Crash Blossoms
-Red Tape Holds Up New BridgesRed Tape delay New BridgesRed Tape to support New Bridges
100%REAL
Dan Jurafsky
Ambiguity is pervasive
Fed raises interest rates
New York Times headline (17 May 2000)
Fed raises interest rates
Fed raises interest rates 0.5%
Dan Jurafsky
non-standard EnglishGreat job @justinbieber! Were SOO PROUD of what youve accomplished! U taught us 2 #neversaynever & you yourself should never give up either♥
segmentation issues idiomsdark horse
get cold feetlose face
throw in the towel
neologismsunfriendRetweet
bromance
tricky entity namesWhere is A Bug’s Life playing …Let It Be was recorded …… a mutation on the for gene …
world knowledge
Mary and Sue are sisters.Mary and Sue are mothers.
But that’s what makes it fun!
the New York-New Haven Railroadthe New York-New Haven Railroad
Why else is making natural language understanding difficult?
Dan Jurafsky
Making progress on this problem…• The task is difficult! What tools do we need?
• Knowledge about language• Knowledge about the world• A way to combine knowledge sources
• How we generally do this:• probabilistic models built from language data• P(“maison” “house”) high• P(“L’avocat général” “the general avocado”) low
Dan Jurafsky
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• To summarize, the knowledge of language needed to engage in complex, language behavior can be separated into six distinct categories:
1-Phonetics and Phonology – The study of linguistic sounds. 2-Morphology – The study of the meaningful components of words. 3-Syntax – The study of the structural relationships between words. 4-Semantics – The study of meaning. 5-Pragmatics – The study of how language is used to accomplish goals. 6-Discourse – The study of linguistic units larger than a single utterance.
Dan Jurafsky
This class
• Teaches key theory and methods for statistical NLP:• Viterbi• Naïve Bayes, Maxent classifiers• N-gram language modeling• Statistical Parsing• Inverted index, tf-idf, vector models of meaning