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FROM SENTENCE STRUCTURE TO “IMMEDIATE” DISCOURSE STRUCTURE: ANNOTATION OF DISCOURSE CONNECTIVES AND THEIR ARGUMENTS Aravind K. Joshi University of Pennsylvania Philadelphia, PA USA IIT, Powai, Mumbai, December 30 2005. Outline. Introduction

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slide1

FROM SENTENCE STRUCTURE

TO

“IMMEDIATE” DISCOURSE STRUCTURE:

ANNOTATION

OF

DISCOURSE CONNECTIVES

AND

THEIR ARGUMENTS

Aravind K. Joshi

University of Pennsylvania

Philadelphia, PA USA

IIT, Powai, Mumbai, December 30 2005

slide2

Outline

  • Introduction
    • Transition from sentence to immediate discourse
  • Dependencies in discourse structure
  • Penn Discourse Treebank (PDTB)
    • Some properties of discourse connectives
    • Some examples from PDTB
    • Some aspects of annotation guidelines
    • Semantics of discourse connectives
      • Assigning roles to the arguments
    • Attributions of arguments and connectives
  • Summary
slide3

Transition from sentence to immediate discourse

  • How much information can be packaged in a sentence?
  • When does a transition from a sentence to discourse happen?
  • Are there any general principles?
    • Beyond some conventions of styleare there any linguistic principles to this transition?
slide4

Transition from sentence to immediate discourse

  • Sentences are made up of clauses
    • Clause: Predicate (Verb) Arguments, Adjuncts
      • Dependency structure
    • Connectives
    • Composition operations
  • Extend dependency structures to discourse
    • Extend the same composition operations to discourse
  • Extend the sentence level parser to discourse
slide5

Transition from sentence to immediate discourse

  • At the sentence level
    • Predicates have as their arguments -- NPs -- NPs and clauses -- Clauses
  • Discourse connectives can be treated as higher order predicates taking only clauses as their arguments
slide6

Sentence Structure and Discourse Structure

  • At the sentence level
    • Structural composition and associated semantic composition
    • Anaphoric links
    • Other inferences
  • At the discourse level
    • Structural composition and associated semantic composition
    • Anaphoric links
    • Other inferences
  • Conventionally, work in discourse structure does not consider and therefore, allow such a decomposition
slide7

Dependencies in discourse structure

  • Discourse connectives as predicates taking clausal arguments
    • The dependencies between the predicate and their arguments can be stretched

Nested Dependencies:

On the one hand, Fred likes beans.

Not only does he eat them for dinner.

But he also eats them for breakfast and snacks.

On the other hand, he’s allergic to them.

slide8

Dependencies in discourse structure

  • Dependencies can be stretched by nesting
  • Crossed dependencies do not seem to be possible
    • Is this cross-linguistically valid?
    • Apparent crossing dependencies are resolved by treating one argument of a discourse connective as anaphoric

Webber, Joshi, Stone, and Knott. 2003. Anaphora and discoursestructure. Computational Linguistics, 29:545-587.

slide9

Crossed dependencies

True crossed dependencies do not seem to be possible

On the one hand, Fred likes beans.

Not only does he eat them for dinner.

But he also eats them for breakfast and snacks.

On the other hand, he’s allergic to them.

*

On the one hand, Fred likes beans.

Not only does he eat them for dinner.

On the other hand, he’s allergic to them.

But he also eats them for breakfast and snacks

In this sense, discourse structure may be simpler than sentencestructure, even cross-linguistically?

slide10

Dependencies in discourse structure

(a) John loves Barolo.

(b) So he ordered three cases of the ’97.

(c) But he had to cancel the order

(d) Becausethen he discovered he was broke.

because gets its arguments from (c) and (d)

then gets its arguments from (b) and (d),

thus crossing the connection between (c) and (d)

associated with because

Apparent crossing dependency: Treat the argument from (b) for then as anaphoric

slide11

Penn Discourse Treebank: PDTB

  • Annotate discourse connectives and their argument structure for the Penn Treebank corpus– PDTB
    • Independent of the specifics of the discourse lexicalized TAG (DLTAG)

People: Aravind Joshi

Eleni Miltsakaki, Rashmi Prasad

Annotators

Collaborator: Bonnie Webber (Edinburgh University)

slide12

PDTB

  • Discourse connectives such as -- and, or, but, because, since, while, when, however, instead, although, also, for example, then, so that, insofar as, nonetheless, … , Empty Connectives
  • -- Subordinate conjunctions, Coordinate conjunctions,
  • Adverbial connectives, Implicit connectives
  • -- Discourse connectives take clauses as their arguments
  • and express relations between clauses, i.e., relations
  • between propositions, events, situations, …
  • associated with the clauses
slide13

Towards computing a class of inferences associated with discourse connectives, hence relevant to complex NLP tasks – IE, MT, QA …

  • Towards discourse structure - discourse understanding
  • Research Strategy
  • Not shallow vs deep syntactic processing
  • Not shallow vs deep semantic processing
  • But
  • Deeper and deeper shallow processing
slide14

Some properties of discourse connectives

  • Discourse connectives have argument structure (analogous to verbs and their argument structure) as in the Propbank. However, there are crucial differences
    • arity of connectives is fixed, they are binary (some apparent exceptions)
    • One argument is in the same sentence in which the connective appears. The other argument may or may not be in the same sentence. It can be in the preceding or following discourse
    • Harder to annotate the extent of an argument
      • one of the arguments can be anaphoric
    • Very little is known about the semantics of discourse connectives
slide15

What is being annotated

?

  • Relation: Connective--explicit or implicit
  • Arguments: Arg1, Arg2
  • Attributions of arguments
  • Attribution of relation
  • Sense of the connective
  • Supplementary material
slide16

Some Examples from PDTB

Subordinate: because

[The federal government suspended sales of U.S. savings

Bonds] because [Congress hasn’t lifted the ceiling on government debt.]

  • Both arguments are in the same sentence

Subordinate: although

Although [started in 1965], [Wedtech didn’t really get

Rolling until 1975] (when Mr. Neuberger discovered the

Federal Government’s Section 8(A) minority business

Program).

  • Both arguments are in the same sentence, one argument has
  • possible supplementary material in ( )
slide17

Adverbial: however

[Both Newsweek and U.S. News have been gaining circulation in recent years without heavy use of electronicgiveaways to subscribers, such as telephone or watches.]

However, [none of the big three weeklies recordedcirculation gains recently.]

  • The two arguments are in different sentences
slide18

Adverbial: for example

[The computers were crude by today’s standards.]

[Apple II owners, for example, had to use their television|sets as screens and stored data on audiocassetts.]

[The computers were crude by today’s standards.]

[Apple II owners, for example, had to use their televisionsets as screens and stored data on audiocassetts.]

  • An argument can be a discontiguous string
  • Problems with aligning arguments with Penn Treebank constituents
slide19

Discourse adverbials as anaphors: Instead

John wanted to eat a pear. Instead he ate an apple.

John will noteat fruit. Instead, he eats only candy bars and potato chips.

John ate an apple. #Instead he wanted a pear.

Antecedent of instead: salient but unchosen orunrealized alternative -- anaphoric argument of insteadLicensing environment: modal context, negation, …

slide20

Adverbial: still

[Some senior advisors argue that with further fights overa capital-gains tax cut and a budget-reduction bill Mr.Bush already has enough pending confrontations withcongress. They prefer to put off the line-item veto untilat least next year.]

Still, [Mr. Bush and some other aides are strongly drawnto the idea of trying out a line-item veto.]

ARG1: Some senior… congress. They prefer…next year

ARG2: Mr. Bush…a line-item veto

ARG1 has two sentences

slide21

Adverbial: also

[On the Big Board, Crawford & Co., Atlanta, (CFD)begins trading today.] Crawford evaluates health careplans, manages medical and disability aspects of worker’scompensation injuries and is involved in claims

adjustments for insurance companies.

Also, [beginning trading today on the Big Board are ElPaso Refinery Limited Partnership, El Paso, Texas, (ELP)and Franklin Multi-Income Trust, San Mateo, Calif.,(FMI).]

  • The sentence (in green) after the left argument of “also” can beregarded as a kind of adjunct of the left argument
  • Discourse connectives have a fixed arity (2).
slide22

Empty connective: EMPTY

[El Paso owns and operates a petroleum refinery.]

EMPTY= whereas [Franklin is a closed-end managementinvestment company.]

  • whereasis the connective that one annotator thought best described the relation expressed by the empty connective
  • Analogous to theempty relation in a noun-noun compoundat the sentence level
slide23

Empty connective

Individuals close to the situation believe Ford officialswill seek a meeting this week with Sir John to outlinetheir proposal for a full bid. <CONSEQUENTLY>Any discussion with Ford could postpone the Jaguar-GM deal, headed for completion within the next two weeks.

slide24

Empty connectives

But now the companies are getting into troublebecause they undertook a record expansion programwhile they were raising prices sharply. <CONSEQUENTLY/AS A RESULT> Third-quarter profits fell at several companies.

Disagreement on selected connective but agreementover class

slide25

Empty connectives

British government restrictions prevent any singleshareholder from going beyond 15% before the end of1990 without government permission. <BECAUSE/HOWEVER> The British government, which ownedJaguar until 1984, still holds a controlling “goldenshare” in the company.

Disagreement over connective and also the classes they belong

slide26

Attributions of arguments and relations

Advocates said the 90-cent-an hour rise to $4.25 an hourby April 1991, is too small for the working poor, whileopponents argued that the increase will still hurt small

Businesses and cost many thousands of jobs.

Relation: Connective- while

Arg1: Advocates said…poor

Arg2: opponents … jobs

Attributions: Relation: WA (writer attribution) Arg 1: WA

Arg 2: WA

slide27

Attributions of arguments and relations

Factory orders and construction outlays were largelyflat in September, while purchasing agents saidmanufacturing shrank further in October.

Relation: Connective- while

Arg1: Factory orders… September

Arg2: manufacturing shrank… in October

Attributions:

Relation: WA

Arg1: WA

Arg2: SA (speaker attribution)

slide28

How many discourse connectives in PTB?

Types: about 253

(Subordinating: 32, Coordinating: 4, Adverbial/Anaphoric: 217)

Tokens: about 23,620

(Subordinating: 7011, Coordinating: 6169,

Adverbial/Anaphoric: 10,440)

Empty connectives: Tokens: about 20,000

Types: ??

Total: Tokens: 43,620

slide29

Annotation Guidelines– some comments

  • What counts as a discourse connective? -- in general, discourse connectives convey a relation between states, events, situations, etc.
  • as a result is a discourse connective
  • But in
  • Strangely, conventional wisdom inside the Beltway regards these transfer payments as …
  • “strangely” requires only a single state/event which it classifies in the set of “strange” events. Hence, it is nota discourse connective
  • What counts as an argument?
slide30

Annotation Guidelines– some comments

  • How far does an argument extend?
  • Although [started in 1965], [Wedtech didn’t really getrolling until 1975] (when Mr. Neuberger discovered theFederal Government’s Section 8 minority business
  • Program).
  • “Proper partial overlap”

ARG1: Wedtech didn’t really … 1975

ARG2: started in 1965

SUP2: when Mr. Neuberger … Program

slide31

Multiple annotations

  • In the standard annotation paradigm only one annotation is selected
  • At the discourse level multiple annotations cannot be completely avoided

[Big bear doesn’t care for disposable diapers,] which aren’t biodegradable. Yet [parents demand them.]

Big bear doesn’t care for disposable diapers, [whicharen’t biodegradable.] Yet [parents demand them.]

slide32

Assigning roles to the arguments

  • For verbs
  • In terms of general roles such as agent, theme, goal, instrument, …
  • In terms of word specific roles
  • He wouldn’t acceptanything of value from those he was writing aboutREL: accept Arg0: acceptor
  • Arg1: thing accepted Arg2: accepted-from
  • Prague Dependency Treebank (PDB) (1998, 2001), Framenet (2000, 2002),
  • Propbank (2002, 2003)
slide33

Assigning “roles” to the arguments of a connective

  • In terms of general roles-- ???
  • In terms of connective specific “roles”
slide34

Roles of arguments of “if” (conditional)

if (hypothetical)

IfJohn studies hardhe will pass the examination

REL: if (hypothetical)

ARG0: (Truth condition)

circumstances which make ARG1 true

ARG1: (Assertion)

expresses assertion

slide35

Roles of arguments of “if” (relevance conditional)

if (relevance)

Ifyou are thirsty,there is beer in the fridge

REL: if (relevance conditional)

ARG0: (Relevance condition)

circumstances in which ARG1 is relevant

ARG1: (Assertion)

expresses assertion

slide36

Roles of arguments of “if” (factual conditional)

if (factual)

If Bill is so unhappy here, he should leave

REL: if (factual conditional)

ARG0: (Factual condition)

someone other than the speaker believes that ARG0 is true and ARG0 justifies ARG1

ARG1: (Conditional assertion)

expresses assertion

slide37

Some possible new senses for if

[It will be at their peril] if [Americans allow another happening like the degrading Bork confirmationcircus]

ARG1: it will … peril

ARG2: Americans … circus

ARG 1 makes reference to ARG 2

If here is not hypothetical conditional but it is just a way of making an assertion, much like hypothetical relevance conditional but not quite like it.

slide38

Some possible new senses for if

[Don’t leave home without the American Express cardif [you’d really rather have a Buick.]

If here is more like the hypothetical relevanceconditional but not quite like it.

slide39

Some possible senses for while

[Under Chapter 11, a company operates under protectionfrom creditors’ lawsuits] while [it works out a planto pay its debts.]

ARG1: Under … lawsuits

ARG2: it works … debts

Con: while

Sense: Temporal

[Some will likely be offered severance package] while[others will be transferred to overseas operations.]

Sense: Concessive

slide40

Some possible senses for while

[Each company remains independent] while [working

together to market and sell their products.]

Sense: Temporal/Concessive

While [the insurance index fell 3.56 to 528.56,] [the Nasdaq bank index fell 5.00 to 432.61.]

Sense: ? Compare but no real contrast

slide41

Some possible senses for since, when, …

  • Senses for since: Temporal, Causal, Temporal/Causal
  • Senses for when: Temporal, Causal, Temporal/Causal
since
Since
  • Temporal (T)
    • She hasn’t played any music since the earthquake hit.
  • Causal (C)
    • Since the budget measures cash flow, a new $1 direct loan is treated as a $1 expenditure.
  • Temporal/Causal (T/C)
    • … and domestic car sales have plunged 19% since the Big Three ended many of their programs Sept 30.
while
While
  • Temporal (T)
    • A nurse contracted the virus while injecting an AIDS patient
  • Concession (Con)
    • The basket product, while it has got off to a slow start, is being supported by some firms.
  • Opposition (Opp)
    • … one ex-player claims he received $4000 to $5000 for his season football tickets while others said theirs brought only a few hundred dollars.
slide44
When
  • Temporal
    • The San Francisco earthquake hit when resources in the field already were stretched
  • Temporal/Causal
    • When the Trinity Repertory Theatre named Anne Bogart as its artistic director last spring, the nation’s theatrical cognoscenti arched a collective eyebrow
slide45

Summary

  • Expected date of release – April 2006
  • -- all explicit connectives (adjudicated)
  • -- all implicit connectives but only about 50% adjudicated
  • -- some annotation senses
  • All connectives, all senses, and some experimental results – December 2006
slide46

Summary

  • Boundary between sentence and discourse
    • Flexible
    • Discourse connectives sit at this boundary
    • Similarities and differences between sentence structure and local discourse structure
  • Properties of discourse connectives
    • Arguments of connectives, a-rity is 2
    • Extent of the arguments and their semantics
    • Annotations of attributions
    • -- Mismatch between syntax and discourse
    • Sense annotation—new opportunities
    • Multiple annotations-- implications