aquaint workshop june 2002 computational implicatures for advanced question answering sanda...

AQUAINT Workshop June 2002

Computational Implicatures for Advanced Question Answering

Sanda Harabagiu

University of Texas at DallasUniversity of Texas at Dallas

AQUAINT Workshop June 2002 - ImpliQA

The Problem

A professional analyst cannot separate his/her intentions and beliefs from the formulation of a question.

Sometimes the analyst makes a proposal or assertion. Implied information, important for the interpretation of a

question. Not recognizable at syntactic or semantic level. Determines the quality of answers returned by the Q/A

system.


Example

“Will Prime Minister Mori survive the crisis?” Implied belief: the position of Prime Minister

is in jeopardy. Problem: none of the question words indicate

directly danger. Question expected answer type: survival Implicature: DANGER


Recognizing the intention of a question

Analyst implication: Camdessus lead IMF, but was succeeded by someone else.

The intention of Q1 was understood.


Novelties of our Model of Question Implicatures

1) Derive all and only the inferences intended by the analyst.

2) Tractable procedures for question. interpretation and coercion of implicatures.

3) Cognitively plausible model of question implicatures.

4) Model diachronically how certain implicatures become semi-conventional.


Using Pragmatic Knowledge for Question Interpretation

Will Prime Minister Mori survive the political crisis? the analyst is not literary meaning

“Will Prime Minister Mori be still alive when the political crisis is over?”

but expresses the belief that

the current political crisis might cost the Japanese Prime Minister his job.


Question Interpretation through Topical Relations

Question: Will Prime Minister Mori survive the political crisis ?

concepts: prime minister, survive, political crisis Problem 1: WordNet encodes political and crisis as two

different concepts Problem 2: semantic ambiguity Problem 3: should we coerce all concepts topically

related to each of the question concepts ? Problem 4: How do we know that the question is literal

or figurative ?


Ideal Derivation of Pragmatic Knowledge


Complete Coercion

prime minister survive political crisis

PERSON

(sense 1)

in England

PERSON

(sense 2)

in other countries

JOB

(sense 3)

unstable situation

crucial stage or turning point

extreme danger

Subject

Select the name entity

Verb Object

Select the most specific

concept: danger


Interpretation via Redundancy

Danger words: resignation, removal, strike, vote – all in political arena“Vote of non-confidence against Prime Minister Mori ”

Need for world knowledge: vote of non-confidence

Danger(vote)

CAUSE: DANGER (Position)

danger(Position)


Method of Generating Automatically Expansion Dictionaries in a Given

Domain

1. Establish the domain: prime minister politician political crisis

2. Use manually created domain taxonomies (e.g. yahoo.com) to collect seed examples of expanded words:

3. Use all WordNet synonyms of all senses of word DANGER: {danger, risk, peril}

ISA

politics

government electionscollect allthe document

documents


Empirical Methods

4.1. Generate word windows centered around each occurrence of a DANGER-word (WINDOW SIZE=200 words)

4.2. Order by frequency of the stem all content words from all windows

4.3 Select the 5 most frequent nouns

4.4 Let PFreq indicate their frequency in the Yahoo documents

4.5 Use each noun with any DANGER word to formulate a query for Google

4.6. Compute the frequency SFreq with which these words occurred as Subjects or OBJECTS in the documents returned by Google


Expand the Dictionary

1. Compute P = for each candidate wordif (SFreq 3) or (SFreq 2) and (P 0.1) add the word to

the dictionary2. Establish a relation with the other concepts of the question.

Example: DANGER(relation) = R

3. Compute a semantic density measure between the new danger word and the different senses of the question concept

prime minister voteR

question concept new DANGER word

PFreq

SFreq


Semantic Density

Measured by the density of common words between the hierarchies of Cq (the question concept) and CN (new word from dictionary)

)log(),(

q

cc

kk

qN Csdescendent

wCCDensity

where cc is the number of common content words occurring in the glosses of the WordNet subhierarchies of CN and Cq


Resolution of Relation

Density (vote, {position, job})

> Density (vote, {person})

DANGER (vote) |– DANGER(position)


Question Interpretation

“Will Prime Minister Mori survive the political crisis”

Q’: Will Prime Minister Mori ‘s position be endangered by the political crisis ?

Q’’: How will Prim Minister Mori’s position be affected by the political crisis?

no moresurviveverb


Linguistic Phenomenon: Metonymy

Referential metonymies The ham sandwich is waiting for his check (Lakoff & Johnson) (Q1) Which wide-body jets serve dinner?

Predicative metonymies The car drinks gasoline (Wilks) (Q2) Which airlines fly from Boston to Denver? (ATIS domain)


Implications as metonymies

How will George W. Bush revive the economy?

In a bid to revive the US economy , President George W Bush has called for his sweeping tax cutting plans to take effect from the beginning of this year , saying 'I strongly believe that a tax relief plan is an important part of helping our country 's economy recover , and I think expediting money into people 's pockets is going to be a key ingredient ...

What feeds teenage violence?

Anger at the system , that universal aspect of teenage rebellion , and probably the central driving force , building a macho cool reputation…


Knowledge Coercion


Metonymic functions

Container for contents The kettle is boiling

Producer for product He bought a Ford.

Object used for user The buses are on strike.

Artist for art form Ted is playing Bach.


Pragmatics of Q/A


Immediate plans

Methods for detecting figurative senses of questions

sortal constraintsselectional restrictions redundant patterns

Methods for coercing the implied knowledgeepistemic logicWeb as a KB – cotraining methods for rapid

knowledge formation


Thank You !Thank You !

aquaint workshop june 2002 computational implicatures for advanced question answering sanda...

Documents

aquaint workshop

impliqa slide

danger slide

question concepts

impliqa interpretation

question words

political crisis problem

advanced question