S.C. Shapiro

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Knowledge Representation for Natural Language Competence

Stuart C. Shapiro

Department of Computer Science and Engineering

and Center for Cognitive Science

State University of New York at Buffalo

shapiro@cse.buffalo.edu

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Motivation

• Deep understanding of NL texts requires a Knowledge Representation & Reasoning formalism/system.

• A variety of logic.

• But not the logic for metamathematics.

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Preview

• I will discuss several issues in KRR for NL Competence,

• Illustrated by interactions with a computational agent.

• Agent: Cassie.

• KRR system: SNePS.

• Interactions are transcribed from consecutive interactions in a single session.

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Interaction with CassieEnglish

(Statement, Question, Command)

(Current) Set of Beliefs[SNePS]

(Updated) Setof Beliefs[SNePS]

Actions[SNeRE]

(New Belief)[SNePS]

English sentence expressingnew belief answering question reporting actions

Answer[SNIP]

GATN Parser

GATN Generator

ReasoningClarification DialogueLooking in World

Reasoning

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Outline

• Introduction

• Intensional Entities

• Complex Categories

• Possession I

• Propositions about Propositions

• Possession II

• Summary

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Intensional Entities 1

• Rather than represent “objects in the world,” represent mental entities.

• Includes Imaginary and Fictional Entities.

• Multiple mental entities may correspond to one world object.– Intensional entities may be co-extensional.– But must be kept separate.

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Intensional Entities 2 : The morning star is the evening star. I understand that the morning star is the evening

star.

: The evening star is Venus. I understand that Venus is the evening star.

: Clark Kent is Superman. I understand that Superman is Clark Kent.

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Intensional Entities 3: Lois Lane saw Clark Kent.

I understand that Lois Lane saw Clark Kent.

: Did Lois Lane see Superman?

I don't know.

: Did Lois Lane see Clark Kent?

Yes, Lois Lane saw Clark Kent.

Note Open World Assumption.

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Intensional Entities 4: Superman went to the morning star.

I understand that Superman went to Venus.

: Did Clark Kent go to Venus?

Yes, Superman went to Venus.

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Intensional Entities 5: Buck Rogers went to the evening star.

I understand that Buck Rogers went to Venus.

: Who went to Venus?

Buck Rogers went to Venus

and Superman went to Venus.

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Intensional Entities 6

The morning star The evening star Venus

Superman Clark Kent Buck Rogers

Lois Lane

Go toGo to

See

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Outline

• Introduction

• Intensional Entities

• Complex Categories

• Possession I

• Propositions about Propositions

• Possession II

• Summary

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Complex Categories 1

• Noun Phrases:

<Det> {N | Adj}* N

Understanding of the modification must be left to reasoning.

Example:

orange juice seat

Representation must be left vague.

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: Kevin went to the orange juice seat.

I understand that Kevin went to the orange juice seat.

: Did Kevin go to a seat?

Yes, Kevin went to the orange juice seat.

Complex Categories 2

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: Pat is an excellent teacher. I understand that Pat is an excellent teacher.

: Is Pat a teacher? Yes, Pat is a teacher.

: Lucy is a former teacher. I understand that Lucy is a former teacher.

Complex Categories 3

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: `former' is a negative adjective.

I understand that `former' is a negative adjective.

: Is Lucy a teacher?

No, Lucy is not a teacher.

Complex Categories 4

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PseudoRepresentation of Complex Categories

• Isa(B30, CompCat(orange, CompCat(juice, seat)))

• Isa(Pat, CompCat(excellent, teacher))

• Isa(Lucy, CompCat(former, teacher))

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Outline

• Introduction

• Intensional Entities

• Complex Categories

• Possession I

• Propositions about Propositions

• Possession II

• Summary

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Possession I.1

• “One man’s meat is another man’s poison.”

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: Richard's meat is Henry's poison. I understand that Henry's poison is Richard's

meat.

: Edward ate Richard's meat. I understand that Edward ate Richard's meat.

: Did Edward eat Henry's poison? Yes, Edward ate Henry's poison.

Possession I.2

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: Did Edward eat Henry’s meat? I don’t know.

: Did Edward eat Richard's poison? I don’t know.

Possession I.3

Moral: Possession is a three-place relation.

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PseudoRepresentation of Possession

• Has(Richard, meat, B35)

• Has(Henry, poison, B37)

• Equiv(B35, B37)

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Outline

• Introduction

• Intensional Entities

• Complex Categories

• Possession I

• Propositions about Propositions

• Possession II

• Summary

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Propositions about Propositions 1

• Propositions are “first-class” mental entities.

• They can be discussed, just like other mental entities.

• And must be represented like other mental entities.

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: That Bill is sweet is Mary's favorite proposition.

I understand that Mary's favorite proposition is that Bill is sweet.

: Mike believes Mary's favorite proposition.

I understand that Mike believes that Bill is sweet.

Propositions about Propositions 2

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: That Mary's favorite proposition is that Bill is sweet is cute.

I understand that that Mary's favorite proposition is that Bill is sweet is cute.

Propositions about Propositions 3

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Representing Propositions

• Representation of Proposition

– Not by a Logical Sentence

– But by a Functional Term

– Denoting a Proposition.

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PseudoRepresentation of Propositions about Propositions

• Has(Mary, CompCat(favorite, proposition), HasProp(Bill, sweet))

• Believes(Mike, HasProp(Bill, sweet))

• HasProp(Has(Mary,

CompCat(favorite, proposition), HasProp(Bill, sweet)),

cute)

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Outline

• Introduction

• Intensional Entities

• Complex Categories

• Possession I

• Propositions about Propositions

• Possession II

• Summary

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Possession II.1• Examples from J. Lyons, Semantics I, 1977,

p. 312,• of inalienable possessive constructions:

“John’s right arm”• of alienable possessive constructions:

“John’s book”

• Use vague representationwith later reasoning.

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: Caren held Stu's hand.

I understand that Caren held Stu's hand.

: Mary held Bill's book.

I understand that Mary held Bill's book.

Possession II.2

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: What is an inalienable possession?

I don't know.

: What is an alienable possession?

I don't know.

Possession II.3

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: Hands are body parts.

I understand that hands are body parts.

: Books are ownable objects.

I understand that books are ownable objects.

Possession II.4

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: What is Stu's hand?

Stu’s hand is the hand.

: What is Bill's book?

Bill’s book is the book.

Possession II.5

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: What is an inalienable possession?

That Stu has a hand is the inalienable possession.

: What is an alienable possession?

That Bill has a book is the alienable possession.

Possession II.6

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PseudoRepresentation of Possession

• Has(Stu, hand, B47) • Has(Bill, book, B49)• Held(Caren, B47)• Held(Mary, B49)• Isa(Has(Stu, hand, B47),

CompCat(inalienable, possession))• Isa(Has(Bill, book, B49),

CompCat(alienable, possession))

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Outline

• Introduction

• Intensional Entities

• Complex Categories

• Possession I

• Propositions about Propositions

• Possession II

• Summary

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Summary• Represent intensional (mental) entities.• Open World Assumption• Vague representation of complex categories.

– Clarified by reasoning.

• Ability to discuss words.– NL is its own metalanguage.

• Possession as a three-place relation.• Propositions as first-class entities.• Vague representation of possession.

– Clarified by reasoning.

• Supplying taxonomy via NL inputs.

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SNePS Research GroupCurrent Members

• Faculty:Stuart C. Shapiro, DirectorWilliam J. Rapaport, Associate DirectorCarl AlphonceJean-Pierre A. KoenigDavid R. Pierce

• Graduate Students:Marc Broklawski Bharat BhushanDebra T. Burhans Haythem O. IsmailFrances L. Johnson John F. Santore

S.C. Shapiro

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For More Information

• URL: http://www.cse.buffalo.edu/~shapiro/

• Group: http://www.cse.buffalo.edu/sneps/