possible extensions to the pdtb and related researchpdtb2012/assets/... · 2012. 5. 24. · (6)...

Possible Extensions to the PDTB and Related Research

Rashmi Prasad, Bonnie Webber, Aravind Joshi

May 1, 2012

PDTB Workshop

University of Pennsylvania

• Planned Extensions to the PDTB (more of a wish list!)

– New Relations: Expanding the coverage for completeness

– Refinements/modifications to existing scheme

• Some Research Topics with the extended PDTB

5/24/2012 PDTB Extensions 2

Introduction

New Relations:

Expanding PDTB Coverage for Completeness


The Sept. 25 “Tracking Travel” column advises readers to “Charge With Caution When Traveling Abroad” because credit-card companies charge 1% to convert foreign-currency expenditures into dollars. In fact, this is the best bargain available to someone traveling abroad.

(Implicit=because) (Contingency:Pragmatic Cause)

In contrast to the 1% conversion fee charged by Visa, foreign-currency dealers routinely charge 7% or more to convert U.S. dollars into foreign currency.


Relations Across Paragraphs

Currently, annotated intra-sentential relations include:

Explicit relations anchored by explicit connectives

(All subordinating, coordinating conjunctions & adverbs)

Implicit relations between clauses separated by a semi-colon:

In mid-October, Time magazine lowered its guaranteed circulation rate base for 1990 while not increasing ad page rates ; (Implicit=thus) with a lower circulation base, Time's ad rate will be effectively 7.5% higher per subscriber; (Cause:Result)


Intra-sentential Relations

But there are several other intra-sentential relations that remain unaccounted for:

(1) Implicit relations associated with colons: But don't breathe too easy : (Implicit=because) Those dividend increases may signal trouble ahead for stock prices, some analysts warn. (Cause:reason)

(2) Implicit relations associated with free adjuncts: The market for export financing was liberalized in the mid-1980s, (implicit=thereby) forcing the bank to face competition. (Cause:result)

Other sentence-internal punctuation as well (dashes, parentheses)



(3) Sentential Relatives: A successor wasn't named, which fueled speculation that Mr. Bernstein may have clashed with S.I. Newhouse Jr. … (Cause:result)

AltLex

The Soviet Union wants much of it delivered by January, which would be a strain in most years.

EntRel



(4) AltLex Expressions

The last federal execution before the Supreme Court's 1972 ruling banning the death penalty took place in 1963, meaning that the federal government didn't exercise its execution authority for eight years.

(Restatement:equivalence)

But I had expected more, which is one reason I began looking at evidence suggesting defects in the official output estimates. (Contingency:Result)

Others: which is why, which is how, which means



Generalization for free adjuncts and sentential relatives:

(a)Any AltLex of the form:

“That/This is why/how…”

“This/That means/meant…”

can appear as a sentential relative:

“…, which is why/how..”

“…, which means..”

(b) Any AltLex of the form:

“This/That <non-copular> verb>…”

can appear as a free adjunct (with present/past participle):

“…, meaning that…”

“…, triggered…”



(5) Subordinators

The company said it made the purchase in order to locally produce hydraulically operated shovels. (Contingency:Purpose)



(5) Subordinators (Cont.) The trend toward lower rents may seem surprising given that some communities in New York are bemoaning the loss of favorite local businesses to high rents. (Contingency:Cause)

All of this is what history will note, assuming that events don't make it seem a bad joke, when the record of this time is put down. (Contingency:Condition) But the shah still kept leaping out at Cap, so Cap bought a hundred merchant ships more and $7 billion of loading barges, ramps, etc., in order that those seven new Army divisions and three Marine brigades could unload from all those new ships and aircraft and go to war in the Zagros mountains. (Contingency:Purpose)



(5) Subordinators (Cont.)

Instead of being just an ad agency, he said: "We have redefined our mission here.”

As a result of dropping the liquidation plan, shareholders will have to treat dividends received this year as ordinary income or capital gains rather than as tax free returns of capital, the company said



(5) Other (free) subordinators:

Reed International, a U.K. publishing group, gained 15 to 397 despite reporting a 3.7% drop in interim pretax profit.



(6) Syntactic Constructions: inverted conditionals Had the contest gone a full seven games, ABC could have reaped an extra $10 million in ad sales on the seventh game alone, … (Contingency:Condition)

Had the suit been filed in time, they said, "Bare-Faced Messiah" would have been suppressed.

(Contingency:Condition)

Other syntactic constructions? Not clear how the expression of the relation can be Indicated for syntactic constructions.



(1) Inter-S Subordinators

Suppose an investor wants to sell a stock, but not for less than $55. A limit order to sell could be entered at that price. (Contingency:Condition) Let's assume that (former Cambodian leader Prince Norodom) Sihanouk does what the press wants him to do and joins up with (Vietnamese-backed Cambodian leader) Hun Sen. Is the trouble over? Can Sihanouk and Hun Sen knock off the Khmer Rouge still supported by China? (Contingency:Condition)

(2) Identify Additional AltLex expressions and connectives, using for example, back translation methods


Inter-sentential Relations

But they must also assign a price to each of these items as well as to floors, wallcoverings, roofing and siding, to come up with a total value for a house.

To do that, they must think in terms of sheetrock by the square foot, carpeting by the square yard, wallpaper by the roll, molding by the linear foot.


Based on studies on: • sense disambiguation (Pitler et al, 2009; Wellner et

al, 2009, Lin et al, 2009)

• High-level discourse representation (Lee et al, 2008; Webber and Prasad, 2008)

• Interaction of discourse relations with relations in other dimensions (Dinesh et al., 2005)


Refinements to Existing Annotations

Additional sense distinctions

• Purpose

• Similarity

• General treatment of pragmatic relations involving inferences over argument content


Senses

Minimality Principle “Only as much text should be selected as the argument as was necessary for the interpretation of the relation. Any additional text that was perceived as relevant but not necessary should be annotated as supplementary material, as Sup1 for material relevant to Arg1, and as Sup2 for material relevant to Arg2.” (SUP helped to boost agreement)

By most measures, the nation’s industrial sector is now growing very slowly – if at all. (Sup1 Factory payrolls fell in September. So did the Federal Reserve Board’s industrial-production index.) Yet many economists aren’t predicting that the economy is about to slip into recession. (Comparison:Concession:Contra-expectation)

SUP annotation was optional, and in many cases, there are no SUPS associated with one or both arguments of a relation


Supplements to Arguments

However, SUP can shed light on useful notions of subordination and coordination in discourse and in relation to higher-level discourse structure (Bluhdorn, 2007), which may correlate with needs of summarization methods.

Or, Background? (SDRT, Asher) Satellite? (RST)

Recast SUP annotation in terms of such notions and define it precisely in terms of its relation to an argument.

For all non-adjacent arguments, is all or any of the intervening material subordinated to any of the arguments?

Make SUP annotation obligatory



Intervening material not annotated as SUP:

AT&T applauded the FCC's actions. "The time is long overdue to take a look at the fierce competition in the long-distance business and the rules governing it," the New York telecommunications firm said in a statement.

But MCI, of Washington, was displeased with the FCC decision concerning Tariff 12, arguing that "AT&T cannot be allowed to flaunt FCC rules.”



• Not annotated as SUP. Are ALL sentences subordinated?

Mr. Boren even spies a silver lining.

He figures the episode will help "clarify any ambiguities" between the committee and administration.

He points to a letter on his desk, his second in a week from President Bush, saying that they "don't disagree." More broadly, Mr. Boren hopes that Panama will shock Washington out of its fear of using military power. "Maybe this will jolt us out of the post-Vietnam syndrome that we never are prepared to use force," he says.

Maybe -- if every senator shared the principles of Mr. Boren.

But it's just as plausible to argue that if even David Boren can get mired in this sort of mess, the problem goes beyond legal interpretation



• If the light is red, stop, because otherwise you’ll get a ticket.

But, the following is not annotated:

• If the light is red, stop. (Implicit=because) Otherwise you’ll get a ticket.

Task will involve identifying those existing relations which are anchored on discourse adverbials as the explicit connectives, and whose arguments belong in different sentences.


Inter-S Implicits in addition to Expicits

We lived in rural areas many years, but now live in St. Louis County, Mo. (EntRel)

This morning as I drove the 13 miles to my law office and endured the routine heavy traffic during that twice-daily journey, I thought of how fortunate it was that we made the decision to be residents of an expanding community with so many opportunities and where so much is happening

Further specify the BASIS for the EntRel relation: individual, event, bridging


EntRel

Possible Research Topics with the extended PDTB


• Range of the different ways in which discourse relations can be realized across languages, and what we can learn from it, e.g., if we can explain the forms based on more general lexico-syntactic properties of a language.

• Properties of PDTB type annotations in some specific domains (biomedical literature, clinical texts, dialogues) and deeper analysis

• Distribution of relation types across languages (explicit vs. implicit)

• Realization of discourse relations through a text: correlation with higher-level document structure (for eg. Structure of scientific articles).

– Different document types (e.g., biomedical literature)


Research Topics

• Relax syntactic analysis to make annotation in other dimension easier.

– How much flexibility can be admitted without losing important information about syntactic relations, what would be the nature of such syntactic representation, and how feasible would such annotation be?


Research Topics

• Paraphrasing

Consider discourse relations and the different ways in which each relation (e.g., reason, chosen alternative) is realized to determine paraphrase patterns.

Identify whether possible paraphrases are constrained in any way

Great value for textual entailment, text generation and machine translation.


Research Topics

Thank You


possible extensions to the pdtb and related researchpdtb2012/assets/... · 2012. 5. 24. · (6)...

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