prepositional phrase attachment problem
Download
Skip this Video
Download Presentation
Prepositional Phrase Attachment Problem

Loading in 2 Seconds...

play fullscreen
1 / 25

Prepositional Phrase Attachment Problem - PowerPoint PPT Presentation


  • 225 Views
  • Uploaded on

Prepositional Phrase Attachment Problem. 03M05601 Ashish Almeida. Overview. Introduction to NLP Analysis in UNL system Prepositional phrase attachment problem Proposed method to handle this problem. Motivation. Analysis involves many complex problems

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Prepositional Phrase Attachment Problem' - addison


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
prepositional phrase attachment problem
Prepositional Phrase Attachment Problem

03M05601

Ashish Almeida

PP attachment problem

overview
Overview
  • Introduction to NLP
  • Analysis in UNL system
  • Prepositional phrase attachment problem
  • Proposed method to handle this problem

PP attachment problem

motivation
Motivation
  • Analysis involves many complex problems
  • Prepositional phrase attachment problem is one such difficult problem.
  • If solved, improve the quality of information extracted manifold
  • No existing system solves the problem

PP attachment problem

tasks involved in nlp

NL understanding

Text

Meaning

NL generation

Tasks involved in NLP

Analysis and generation

PP attachment problem

phases in nlp
Phases in NLP
  • Morphological analysis
  • Syntactic analysis
  • Semantic analysis
  • Discourse integration
  • Pragmatic analysis

PP attachment problem

is nl compositional
Is NL Compositional ?
  • Compsitional expression
    • Meaning of the whole from meaning of parts

e.g. strong tea

-rich tea

day by day

- all the time

PP attachment problem

analysis
Analysis

Morphological + Syntactic + Semantic analysis

  • All these phases are dependent on each other.
  • Interactive Vs modular approach
  • Analysis in UNL system - interactive

PP attachment problem

slide8
UNL …
  • UNL is Interlingua

e.g. Ram ate rice with spoon.

eat(icl>do)

@ entry

@ present

agt

ins

obj

John(iof>person)

spoon(icl>artifact)

rice(icl>food)

PP attachment problem

unl expresion
UNL expresion

UNL Expression for Ram ate rice with spoon.

agt(eat(icl>do)[email protected]@entry, Ram(iof>person))

obj(eat(icl>do)[email protected]@entry, rice(icl>food))

ins(eat(icl>do)[email protected]@entry, spoon(icl>tool))

agt(eat(icl>do)[email protected]@entry, Ram(iof>person))

Relation

UWs

Attributes

PP attachment problem

analysis in unl
Analysis in UNL
  • Enconverter
    • Natural Language to UNL
    • Handles one sentence at a time
    • Predicate preserving parser
    • Kind of Turing machine
  • Components
    • Dictionary : lexical units, uw, semantic attributes
    • Rule base : head movement rules, relation resolving rules
  • Working
    • Uses dictionary and rule bases to process the sentence.

PP attachment problem

prepositional phrase attachment problem11
Prepositional Phrase Attachment Problem
  • Type of Structural ambiguity in a sentence

Verb attachment

JohnNP

readVP

the reportNP

on new technologies.PP

Noun attachment

PP attachment problem

prepositional phrase attachment problem12

read

read

John

the report

John

on

the report

on

new technologies

new technologies

Prepositional Phrase Attachment Problem…
  • Noun attachment Vs verb attachment

e.g. John read the report on new technologies.

*

PP attachment problem

establishing semantic relation
Establishing semantic relation

Same structure-different semantic relation

e.g.

1. Ram ate rice withspoon.……instrument

The UNL for this sentence is

ins(eat(icl>do)[email protected]@entry, spoon(icl>tool))

2. Ram ate rice with Sita. ……co-agent

The UNL for this sentence is

cag(eat(icl>do)[email protected]@entry, Sita(iof>person))

PP attachment problem

difficult problem
Difficult problem
  • PP attachment problem is simpler or no problem for human being

- who use world knowledge to process it.

  • This world knowledge is not available to machines.

e.g. travel by night …time

travel by bus …instrument

PP attachment problem

different sites of attachment
Different sites of attachment
    • The searchforthe policy is going on.
    • The test will be held at the endofAugust.
    • InAugust 1947, India became free from British rule.
    • Wilson received a medal from the commanding officerata farewell party.
  • There is no restriction on how far the PP can lie from the word to which it relates.

PP attachment problem

affinity with preceding phrase
Affinity with preceding phrase
  • The preposition ofgets attached to a noun phrase or a verb phrase immediately preceding it.
    • They were involved in the murder of a 90-year-old woman.
    • It was begun last week by the crew of a giant crane-barge.
    • He died of an overdose of sleeping pills
    • The system will be tailored to meet the need of the political party.

PP attachment problem

existing methods
Existing methods
  • generate mod-obj combination for almost all PP relations
    • E.g He came according to his promise.

agt(come(icl>do)@[email protected], he)

*mod(come(icl>do)@[email protected], :01)

obj:01(according to, promise(icl>abstract thing))

mod:01(promise(icl>abstract thing),he)

  • Tags introduced manually to resolve phrase boundaries
    • E.g. It delineates <p>the scope of phrases</p> before <p>conversion of the sentence</p>.

PP attachment problem

related work
Related work
  • Statistical learning methods used
  • Wordnet is used to find relations between words
  • Analysis of corpus is required
  • Not all aspects of problem considered
  • The hypothesis does not apply to all cases

“PP attachments obey the principle of locality”

PP attachment problem

observations

Frequency

Preposition

Poly. count

29391

of

7

18214

in

10

9343

to

8

14

by way of

1

16

by means of

1

Observations
  • Prepositions frequency is calculated from British National Corpus
  • Classified into 2 parts
    • Simple Preposition
    • Ambiguous prepositions

PP attachment problem

addition to semantic attributes hierarchy
Addition to Semantic Attributes hierarchy
  • Semantic attributes required to disambiguate
  • Addition required, if existing attributes fail to classify
  • necessary condition
    • the attributes should be able to classify the semantically separate structures as separate entities.

e.g.the train for Delhi ….to()

the price for the Hill Road pool ….mod()

PP attachment problem

inclusion of preposition in unl expression
Inclusion of preposition in UNL expression
  • a picture on the wall

plc(picture, wall).

  • The cat walked across the street.
    • Wrong UNL

*plc ( walk, street )

-cat walked along the street

-cat walked across the street

    • Correct UNL

plc (walk, :01)

obj:01(across, street)

PP attachment problem

classification based on syntax structure

[ Verb + for + Noun phrase]

v-pur

He was waiting for the rainy day.

v-pur

He applied for a certificate.

[ Noun phrase + for + Noun phrase]

n-mod

The search for the policy is going on.

n-mod

He pays the price for his indulgence.

Classification based on syntax structure
  • Sentences have different syntactic structure
  • Parsing the depends on surface structure

- Active-passive, transitive-di-transitive, present-past participles etc.

  • Classification based on syntax pattern

PP attachment problem

classification based on semantics

Relation

Example sentence

ON

plc

a picture on a wall

ins

to travel on the bus

tim

He came on Sunday

seq

Report to reception on arrival

mod

a book on South Africa

ins

She played a tune on her guitar

plc

You can get me on 0181 530 3906

Classification based on semantics
  • Deciding factors
    • Syntax, attributes, preposition, subcategorisation frame(for verbs)

Partial list of preposition on and its possible semantic relation

PP attachment problem

updating rule base

Comment

;N/abs for N/abs ;search for policy

delete preposition for

DL(N,ABS)

{PRE,#FOR:::}

{N,ABS:+PRERES,+FORRES,+pPUR::}P25;

Comment

;V FOR N-UNIT-QUARES ;suspend for 2 days

Delete preposition for

DL(VRB){PRE,#FOR:::}

{N,UNIT,TIM,QUARES

:+PRERES,+FORRES,+pDUR::}P30;

Updating rule base
  • Simpler if the classification is perfect.
  • Issues involved
    • Priority, proper specification

Two rules showing difference in priority – specific to general

PP attachment problem

conclusion
Conclusion
  • World knowledge is realized in terms of semantic attributes.
  • Phrasal verbs are not considered
  • Idiomatic constructs are not handled

- e.g. day by day

all the time

PP attachment problem

ad