Syntactic Disambiguation Syntactic Disambiguation through through

Lexicon EnrichmentLexicon Enrichment

Second Stage Project Presentation

Guide: Pushpak Bhattacharyya

Ashish Almeida03M05601

April 22, 2023

2

Overview• Motivation• Problem definition• Linguistic theory• Lexical enrichment• Design and implementation• Results• Future work

April 22, 2023

3

Motivation• Robust and scalable UNL generation

required• English analysis for extracting meaning• Correct analysis correct meaning

representation• Identification of correct syntactic

representation• Identification of correct semantic relation

April 22, 2023

4

Preposition Phrase Attachment Problem

• John covered the baby with a blanket.

covered

John the baby with

a blanket

John

covered

the baby

with

a blanket

Wrong !

Verb attachmentNoun attachment

April 22, 2023

5

Universal Networking Language• He forwarded the mail to the minister.

objagt

@ entry @ past

minister(icl>person)

forward(icl>send)

mail(icl>collection)

He(icl>person)

@def

@def

gol

April 22, 2023

6

Linguistic Insights• Syntactic level

– Syntactic Frame– Subcategorization

• Semantic level– Selectional restrictions– Thematic/theta roles

April 22, 2023

7

Syntactic Frame• Sequence of words as they appear in

sentences

– [V-ART-N] … handed a book– [NP-to-NP] ... the mail to the minister– [V-NP-P-NP] … forwarded the mail to the

minister

April 22, 2023

8

Subcategorization• Verbs

– He put the book on the table.– *He put the book.– *He put.

• put: [ _NP PP-on]

• Nouns– his reliance on/*at/*with her help.– *his reliance.

• reliance: [ _PP-on]

• Adjectives– He is fond of reading.

• fond: [ _ PP-of]

April 22, 2023

9

Selectional Restrictions• The boy murdered John.• *The boy murdered the tree.

– Thus the verb ‘murder’ needs a human as object.

• murder: [HUMAN _ HUMAN]

April 22, 2023

10

Thematic Roles• Each argument of verb has a unique role

associated with it.• Each role is assigned to a single argument.

E.g. – The boy murdered John.

• The boy - agent• John - patient/theme

• Other thematic roles : Instrument, locative, goal

• UNL relations: analogous to thematic roles.

April 22, 2023

11

Lexicon Enrichment• Idiosyncratic information

– Subcategorization– Thematic roles in terms of UNL relations

• How to get this information ? – Subcategorization

• Oxford advanced learner’s dictionary, WordNet – UNL relations

• Beth Levin, manual effort

April 22, 2023

12

An Example Dictionary Entry• forward• E.g. he forwarded the mail to the minister• [forward]{}“forward(icl>sent)”

(VRB,VOA,VOA-PHSL, #_TO_A2,#_TO_A2_gol)<E,0,0>;

headword

Universal Word Attributes

April 22, 2023

13

Issues • The work focuses on

– The [V-NP-P-NP] frame– Commonly used prepositions

• In, on, of, with, from, to, for– Disambiguating to– Active voice

April 22, 2023

14

Design• Fill the valency of the nearest element first.• If in the frame [V-N1-P-N2]

– both V and N1 have #P in their subcategorization frames, then satisfy the demand of the nearest element to P, i.e., the noun first.

• Else, give priority to that element which subcategorizes the preposition P

• Else, give priority to the events and actions (can be verb or noun)– destroyV, destructionN etc.

April 22, 2023

15

Summarization of AlgorithmConditions Action

Attributes of

V

Attributes of

NP1

Attributes of

NP2

Attachment of

NP2

Examples

1 #<P> #<P> _ N1 …paid a visit to the museum.

2 #<P> Not#<P>

_V

...passed the ball to Bill. …imposed heavy penalties on fuel

dealers.

3a

Not#<P>

Not#<P>

PLACEV …met him in his office.

TIME …met him in the afternoon.

3b

Not#<P>

Not#<P>,EVENT

PLACEN1

…cancelled a meeting with his friends.TIME

5 Not#<P> #<P> N1 …supplied plans for projects.

April 22, 2023

16

Problems with toto• Infinitival to

– Do not allow onion to brown• Preposition to

– The lights changed from green to brown

Problem:Detect if the lexical element is to-preposition or to-infinitive

April 22, 2023

17

Heuristics to Detect toto-preposition

Criterion Preposition to

Infinitival to

- to is followed by a determiner

- to is followed by a word followed by a plural marker

- to is followed by an adjective

- to is followed by a proper noun

- to is followed by a pronoun

- the matrix verb specifies that it needs a to- preposition complement.

- to is preceded by a noun which specifies that it

needs a to-preposition complement.

- the matrix verb specifies that it needs a to- infinitival complement.

- to is preceded by a noun which specifies that it

needs a to-infinitival complement.

- to is followed by a base verb

April 22, 2023

18

Implementation• Creating new dictionary with extra

attributes• Writing new rules to use these new

attributes– Rules to use subcategorization information– Rules for processing events (nouns and

verbs)

April 22, 2023

19

Analysis Engine (Enconverter)

• Analysis windows– Left Analysis Window (LAW)– Right Analysis Window (RAW)

• Condition windows– Many in number– LCWs, RCWs

LAW

Word2

Word1

Word4

…

RAW

RCWWordnLC

W

Word3

sentence window

s

April 22, 2023

20

Operations in Analysis• Movement of heads• Addition of two nodes• Deletion of a node• Creating relation between two nodes• Adding dynamically inferred attributes

to node

April 22, 2023

21

Rules ; Right shift to affect noun attachment R{VRB,#_FOR_AR2:::}{N,#_FOR:::}(PRE,#FOR)P60;This states that IF

The left analysis window is on a verb which takes a for-pp as the second argument (indicated by #_FOR_AR2)

ANDThe right analysis window is on a noun which takes a for-pp as an argument (indicated by #_FOR)

ANDThe preposition for follows the noun (indicated by (PRE,#FOR) )

THENShift right (indicated by R at the start of the rule) anticipating noun attachment for the PP.

April 22, 2023

22

Other Rules; Create relation between V and N2, after resolving the preposition

preceding N2 <{VRB,#_FOR_AR2,#_FOR_AR2_rsn:::}

{N,FORRES,PRERES::rsn:}P25;

;Delete the preposition ON>(VRB,EVENT,VOA){PRE,#ON:::}

{N,UNIT,TIME,DAY:+ONRES,+PRERES::}P27;

;Create the relation tim between verb and noun<{VRB,VOA:::}

{N,TIME,UNIT,ONRES,PRERES::tim:}P20;

April 22, 2023

23

Testing• Resources:

– British National Corpus– WordNet– Brown corpus

• Filtered out– Phrasal verbs– Compound nouns– Longer sentences

• Semantically different types of constructstested in [V-N-P-N] frame.

April 22, 2023

24

Cases of withwithDifferent semantic Roles in different syntactic and semantic environments

Attachment Semantic relation

Example

Noun obj He cancelled [a meeting with his students].

Noun and She wore [a green skirt with a blouse].

Verb ins He [covered the baby with a blanket].

Verb gol That [provides him with a living].

Verb ptn He [is playing chess with his friend].

April 22, 2023

25

Results for of-preposition

The results of testing for solving PP attachment and generating UNL

Corpus Frames Total no. of Sentences

No. of Correct attachments & UNL relations

Accuracy %

BNC V-N1-of-N2 1000 886 88

WSJ V-N1-of-N2 661 597 90

April 22, 2023

26

Conclusion• Lexical enrichment originating from key

linguistic principles makes the analysis more correct

• Rule-base design simplified due to distinction made between complements and adjuncts during analysis

April 22, 2023

27

Future Work• Handling the alternation patterns of

verbs• Applying the algorithm on all

prepositions

• Extracting the information through various resources – such as dictionaries and annotated corpus

April 22, 2023

28

References• UNDL Foundation: The Universal Networking Language (UNL)

specifications version 3.2. (2003) http://www.unlc.undl.org

• Grimshaw, Jane.: Argument Structure. The MIT Press, Cambridge, Mass. (1990)

• Brill, E. and Resnik, R.: A Rule based approach to Prepositional Phrase Attachment disambiguation. Proc. of the fifteenth International conference on computational linguistics. Kyoto. (1994)

• Levin, Beth.: English verb Classes and Alternation. The University of Chicago Press, Chicago. (1993)

• Hornby, A. S.: Oxford Advanced Learner’s Dictionary of Current English. Oxford University Press, Oxford.(2000)

April 22, 2023

29

Thank youThank you

April 22, 2023

30

Example UNLInI deposited my money in my bank account.{unl}

gol(deposit(icl>put):02.@entry.@past, account(icl>statement):0W)

obj(deposit(icl>put):02.@entry.@past, money(icl>currency):0F)

agt(deposit(icl>fasten):02.@entry.@past, I:0C)mod(money(icl>currency):0F, I:0C)mod(account(icl> statement):0W,

bank(icl>possession):0R)mod(account(icl> statement):0W, I:0O)

{/unl}

April 22, 2023

31

Example UNL

OnI put the book on the table.{unl}

gol(put(icl>move):02.@present.@entry, table(icl>object):0M.@def)obj(put(icl>move):02.@present.@entry, book(icl>publication):0A.@def)agt(put(icl>move):02.@present.@entry, I:00)

{/unl}

April 22, 2023

32

Example UNLToThey served a wonderful meal to fifty delegates.{unl}

gol(serve(icl>provide):05.@entry.@past, delegate(icl>person):12.@pl)

obj(serve(icl>provide):05.@entry.@past, meal(icl>food):0O.@indef)

agt(serve(icl>provide):05.@entry.@past, they(icl>thing):00)

mod(meal(icl>food):0O.@indef, wonderful(mod<thing):0E)

qua(delegate(icl>person):12.@pl, fifty(icl>number):0W)

{/unl}