Upload
vern
View
39
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Syntactic Disambiguation through Lexicon Enrichment. Second Stage Project Presentation Guide: Pushpak Bhattacharyya Ashish Almeida 03M05601. Overview. Motivation Problem definition Linguistic theory Lexical enrichment Design and implementation Results Future work. Motivation. - PowerPoint PPT Presentation
Citation preview
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}