Lecture 1: Welcome to CL

[Thanks to Kathy McKeown, Ellen Riloff and Jimmy Lin for some material and examples.]

Course administrivia: see web page

About This Course

CL versus NLP?

• doing what linguists do to language, with computers
• doing what humans  do to language, with computers
• science versus engineering

Course Goals:

• How can machines recognize and generate text (+ speech)?

Knowledge Needed

Goal: Discover what the speaker meant!
Morphology: word formation

• "Stud tires out"
• is "tires" a noun or verb?
• Web search: union activities in New York
• union/unions?  activities/activity?
• active?  action?  actor?
• New versus New York
• kick => kicks, kicked, kicking
• sit  => sits,  sat,    sitting
• gorge / gorgeous
• glass / glasses
• arm   / army

Syntax: structural relationships between words

• Parts of speech
• The_D boy_N threw_V a_D ball_N to_P the_D brown_J dog_N .
• Time flies like an arrow ?
• Constituent Structure
• John hit Bill.
• Bill was hit by John.
• Bill hit John.
• Bill, John hit.
• Who John hit was Bill.
• Structural ambiguity (attachment)
• Teacher Strikes Idle Kids
• Enraged Cow Injures Farmer With Ax
• I saw the Grand Canyon flying to New York.
• I saw the man on the hill with the telescope.
• Syntax doesn't tell us much about meaning
• Colorless green ideas sleep furiously
• fire match arson hotel
• "dog collar" versus "flea collar"
• plastic cat food can cover

Semantics: word meaning and word composition

• Lexical semantics
• I walked to the BANK ...
•              ... of the river.
•              ... to get money.
• The BUG in the room ...
•              ... flew out the window.
•              ... was planted by spies.
• I work for John Hancock ...
•              ... and he is a good boss.
•              ... which is a good company.
• Scoping issues
• Everyone on the island speaks two languages
• Two languages are spoken by everyone on the island

Discourse: influence of textual context

• Coreference/anaphoricity:
•    [President John F. Kennedy] was assassinated.
•    [The president] was shot yesterday.
•    Relatives said that [John] was a good father.
•    [JFK] was the youngest president in history.
•    [His] family will bury [him] tomorrow.
•    Friends of [the Massachusetts native] will hold a candlelight service in [Mr. Kennedy]'s home town.
• Adding interpretations:
• 1. I only like traveling to Europe.
•     So I submitted a paper to ACL.
• 2. I only like traveling to Europe.
•     Nevertheless, I submitted a paper to ACL.

Pragmatics: influence of context/situation, how we use language to communicate

•   "Going Home" - A Play in One Act

  Scene 1: Pennsylvania Station, NY
             (Hal) Long Beach?
    (Passerby) Downstairs, LIRR Station.

  Scene 2: Ticket Counter, LIRR Station
             (Hal) Long Beach?
          (Clerk) $4.50.

  Scene 3: Information Booth, LIRR Station
             (Hal) Long Beach?
          (Clerk) 4:19, Track 17.

  Scene 4: On the train, vicinity of Forest Hills
             (Hal) Long Beach?
  (Conductor) Change at Jamaica.

  Scene 5: Next train, vicinity of Lynbrook
             (Hal) Long Beach?
  (Conductor) Right after Island Park.

• Rules of Conversation:
• Do you have the time?
• Could I please have the salt?
• Speech Acts
• I bet you $50 that the Nats will win.
• Will you marry me?

World Knowledge: facts about the world at large, common sense

• John went to the diner.
     He ordered steak.
     He left a tip and went home.
• John wanted to commit suicide.
     He got a rope.

Welcome to CMSC 723!

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