Fall 2004

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EECS 595 / LING 541 / SI 661
Natural Language Processing

• Fall 2004
• Lecture Notes 3

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Context-Free Grammarsfor English
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Context-Free Rules and Trees

• Grammars
• CFG PSG BNF
• Derivations, parse trees

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Constituency

• Examples
• Josephine
• My neighbors cat
• He
• Peter, Paul, and Mary
• The first three people to participate in the
  competition
• with (?)
• Preposed and postposed constructions
• In the park, he plays with his dog.
• He plays in the park with his dog.
• He plays with his dog in the park.

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Examples of noun phrases

• Terminals, non-terminals
• Parsing the process of mapping from a string of
  words to one or more parse trees

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Sentence-level constructions

• Declarative vs. imperative sentences
• Imperative sentences S? VP
• Yes-no questions S ? Aux NP VP
• Wh-type questions S ? Wh-NP VP
• Fronting (less frequent)On Tuesday, I would
  like to fly to San Diego

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Noun phrase

• Before the noun
• Determiner a, the, that, this, those, any, some
• No determiner (e.g., in plural, mass nouns
  dinner)
• Predeterminers all
• Postdeterminers cardinals, ordinals,
  quantifiers one, two first, second, next, last,
  past, other, another many, (a) few, several,
  much, a little
• Adjectives a first-class fare, a nonstop flight,
  the longest layover
• AP the least expensive fare
• NP ? (Det) (Card) (Ord) (Quant) (AP) Nominal

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Noun phrases (Contd)

• Postmodifiers
• any stopovers for Delta seven fifty one
• all flights from Cleveland to Newark
• Nominal ? Nominal PP (PP) (PP)
• Non-finite postmodifiers gerundive, -ed,
  infinitive

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Gerunds

• any flights arriving after ten p.m
• Nominal ? Nominal GerundVP
• GerundVP ? GerundV NP GerundV PP GerundV
  GerundV NP PP
• GerundV ? being preferring arriving

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Infinitives and ed forms

• the last flight to arrive in Boston
• I need to have dinner served
• which is the aircraft used by this flight?

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Postnominal relative clauses

• Restrictive relative clauses
• A flight that serves breakfast
• Flights that leave in the morning
• The United flight that arrives in San Jose at ten
  p.m.
• Rules
• Nominal ? Nominal RelClause
• RelClause ? (who that) VP
• Multiple postnominal modifiers can be combined
• A boy from London studying French in Spain
• (what are the modifiers in the previous example)?

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Combining post-modifiers

• A flight from Phoenix to Detroit leaving Monday
  evening
• Evening flights from Nashville to Houston that
  serve dinner

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A slightly more complicated example

• The earliest American Airlines flight that I can
  get
• What rules are needed in the grammar for this
  type of constructions?

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Coordination

• Coordinate noun phrases
• NP ? NP and NP
• S ? S and S
• Similar for VP, etc.

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Agreement

• Examples
• Do any flights stop in Chicago?
• Do I get dinner on this flight?
• Does Delta fly from Atlanta to Boston?
• What flights leave in the morning?
• What flight leave in the morning?
• Rules
• S ? Aux NP VP
• S ? 3sgAux 3sgNP VP
• S ? Non3sgAux Non3sgNP VP
• 3sgAux ? does has can
• non3sgAux ? do have can

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Agreement

• We now need similar rules for pronouns, also for
  number agreement, etc.
• 3SgNP ? (Det) (Card) (Ord) (Quant) (AP) SgNominal
• Non3SgNP ? (Det) (Card) (Ord) (Quant) (AP)
  PlNominal
• SgNominal ? SgNoun SgNoun SgNoun
• etc.

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Combinatorial explosion

• What other phenomena will cause the grammar to
  expand?
• Solution parameterization with feature
  structures (see Chapter 11)

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The Verb phrase

• Vp ? Verb
• VP ? Verb NP
• VP ? Verb NP PP
• VP ? Verb PP

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Sentential complements

• You said there were two flights that were the
  cheapest
• You said you had a two hundred sixty six dollar
  fare
• VP ? Verb S
• I want to fly from Milwaukee to Orlando
• Im trying to find a flight that goes from
  Pittsburgh to Denver next Friday
• VP ? Verb VP

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Subcategorization

• Frames
• 0 eat, sleep
• NP prefer, find, leave
• NP NP show, give
• PPfrom PPto fly, travel
• NP PPwith help, load
• VPto prefer, want, need
• VPbarestem can, would, might
• S mean

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Subcategorization ambiguity

• Find me a flight
• What phenomenon is related to this sentence?
• Others?

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Auxiliaries

• Modals can, could, may, might
• Perfect have
• Progressive be
• Passive be
• What are their subcategories?
• Ordering modal

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Midterm (10/26) reading list

• Chapter 1 Introduction
• Chapter 2 Regular expressions and automata
• Chapter 3 Morphology and finite-state
  transducers FSM tutorial
• Chapter 8 Word classes and POS tagging
• Chapter 9 Context-free grammars for English
• Chapter 10 Parsing with context-free grammars
• Chapter 11 - Features and unification

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Syntaxscape

• Written by Juno Suk of Lucent
• http//www.cs.columbia.edu/radev/syntaxscape/

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(No Transcript)
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Read by yourselves

• 9.9. Spoken language syntex
• 9.10. Grammar equivalence
• 9.11. Finite-state and context-free grammars

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Readings for next time

• JM Chapters 10, 11
• Lecture notes 3