EVENT EXTRACTION

Heng Ji

jih@rpi.eduOctober 4, 2015

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• Event Definition• Event Knowledge Networks Construction• Basic Event Extraction Approach• Advanced Event Extraction Approaches

• Information Redundancy for Inference• Co-training

• Event Attribute Labeling• Event Coreference Resolution• Event Relation• Challenges

Outline

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• State-of-the-art Information Extraction and Knowledge Discovery Techniques are Entity-Centric

• Event-centric Knowledge Discovery from unstructured data to organize knowledge in a network structure

• Construct High-quality Event Networks• Node: an event (a cluster of coreferential event mentions)

• Event Mention Extraction based on Joint Modeling with Structured Prediction

• Event Coreference Resolution based on semantic attributes

• Edge: relation between events• Some are horizontal and some are vertical, forming an event cone

From Entity-Centric to Event-Centric

John Boehner (attendee)

[Title: House SpeakerMember of: Republican

Residence: Ohio]

Obamacare

(act)

Barack Obama(approver)

[Title: PresidentEmployer: US]

2013/10/01Doc2

US government(organization)

CLOSE-ORG

US congress(agent)

2013/10/02Doc3

2013/10/03Doc5

Healthcarereform(cause)

2010/03/03Doc1

SIGN

Obama (attendee)

MEET

Lockheed Martin

(Employer)

3000 Workers

(Employee)

LEAVE

COREFERENCE

COREFERENCE

SUB-EVENT

CAUSAL

2013/10/02Doc4

NSF(organization)

DARPA(organization)

CLOSE-ORG

From Entity-Centric to Event-Centric

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• An Event is a specific occurrence involving participants. • An Event is something that happens. • An Event can frequently be described as a change of state.

Chart from (Dölling, 2011)

Most of current NLP work focused on this

What is an event?

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What is an event?Topic Detection and Tracking (TDT)

Automatic Content Extraction(ACE) & Entities, Relations

and Events (ERE)

Propbank,Nombank Timebank,Discourse Treebank

Temporal order of coarse-grained groups of events (“topics”)

Defined 33 types of events, each event mention

includes a trigger word and arguments with roles

Each predicate is an event type, no argumentsSome nominals and adjectives allowed

Rich semantic roles on concepts, no typing on predicates

Abstract Meaning Representation (AMR)

Chart adapted from (Strassel, 2012)

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• Task Definition• Basic Event Extraction Approach• Advanced Event Extraction Approaches

• Information Redundancy for Inference• Co-training

• Event Attribute Labeling• Event Coreference Resolution

Event Extraction

• An event is specific occurrence that implies a change of states• event trigger: the main word which most clearly expresses an event occurrence• event arguments: the mentions that are involved in an event (participants)• event mention: a phrase or sentence within which an event is described, including

trigger and arguments• Automatic Content Extraction defined 8 types of events, with 33 subtypes

ACE event type/subtype Event Mention Example

Life/Die Kurt Schork died in Sierra Leone yesterday

Transaction/Transfer GM sold the company in Nov 1998 to LLC

Movement/Transport Homeless people have been moved to schools

Business/Start-Org Schweitzer founded a hospital in 1913Conflict/Attack the attack on Gaza killed 13

Contact/Meet Arafat’s cabinet met for 4 hoursPersonnel/Start-Position She later recruited the nursing student

Justice/Arrest Faison was wrongly arrested on suspicion of murder

Event Mention Extraction: Task

triggerArgument, role=victim

• Staged classifiers• Trigger Classifier

• to distinguish event instances from non-events, to classify event instances by type

• Argument Classifier• to distinguish arguments from non-arguments

• Role Classifier• to classify arguments by argument role

• Reportable-Event Classifier• to determine whether there is a reportable event instance

• Can choose any supervised learning methods such as MaxEnt and SVMs

Supervised Event Mention Extraction: Methods

(Ji and Grishman, 2008)

Typical Event Mention Extraction Features Trigger Labeling

Lexical Tokens and POS tags of candidate

trigger and context words

Dictionaries Trigger list, synonym gazetteers

Syntactic the depth of the trigger in the parse tree the path from the node of the trigger to

the root in the parse tree the phrase structure expanded by the

parent node of the trigger the phrase type of the trigger

Entity the entity type of the syntactically

nearest entity to the trigger in the parse tree

the entity type of the physically nearest entity to the trigger in the sentence

Argument Labeling Event type and trigger

Trigger tokens Event type and subtype

Entity Entity type and subtype Head word of the entity mention

Context Context words of the argument

candidate

Syntactic the phrase structure expanding the

parent of the trigger the relative position of the entity

regarding to the trigger (before or after)

the minimal path from the entity to the trigger

the shortest length from the entity to the trigger in the parse tree

(Chen and Ji, 2009)

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OOVthis morning in Michigan, a second straight night and into this morning, hundreds of people have been rioting [attack] in Benton harbor.

Scene understandingThis was the Italian ship that was taken -- that was captured [transfer-ownership] by Palestinian terrorists back in 1985 and some may remember the story of Leon clinghover, he was in a cheal chair and the terrorists shot him and pushed him over the side of the ship into the Mediterranean where he obviously, died. The gloved one claims the label has been releasing new albums and Jackson five merchandise without giving [transfer-money] him "a single dollar." Airlines are getting [transport] flyers to destinations ontime more often. Three Young Boys,ages 2, 5 and 10 survived and are in critical [injure] condition after spending in 18 hours in the cold.

Event Trigger Identification Missing Errors

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Lara hijacking in 1995 has been captured [arrest-jail] by U.S. forces in or near Baghdad. I want to take [transport] this opportunity to stand behind the Mimi and proclaim my solidarity. But when we moved [transport] in closer and started to scan the area, then I saw the 2-year-old waving from next to the airplane. He's left [transport] a lot on the table. Barbara, Bill Bennet's Glam gambling loss [die] changed my opinion. Stewart has found the road to fortune wherever she has traveled [transport]. And it's hard to win back that sort of brand equity that she's lost [end-position].Police measure the spot where ten months old Miana Williams landed after she was thrown [transport] from a seventh floor window at this apartment building. Reason, not result:The baby fell [die] 80 feet. These tree branches cushioned her fall [die] and saved her life.

Event Trigger Identification Spurious Errors

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He -- After landing and taking a brief tour of part of the ship, he also went [transport] out on to the flight deck and observed some of the flight operations of some of the f-18 aircraft that are now leaving these aircraft…still hurts [attack] me to read this.

Metaphor features: semantic categories (noun.animal, noun.cognition) or degree of abstractness

Any farm kid knows that certain animals cannot see for a few days after they're born [born], including puppies. We happen to be at a very nice spot by the beach where this is a chance for people to get [transport] away from CNN coverage, everything, and kind of relax .He bought the machinery, moved [transport] to a new factory, rehired some of the old workers and started heritage programs.Under the reported plans, Blackstone Group would buy Vivendi's theme park division, including Universal Studios Hollywood, Universal Orlando in Florida and Universal's ownership interests in parks in Spain and Japan, a source close to the negotiations [meet] told the paper.

Event Trigger Identification Spurious Errors (Con’t)

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a man in New York is facing attempted murder charges after allegedly throwing [transportattack] his baby seven stories to the ground below. He's also being fined [transfer-money fine] $3 million and was ordered to pay $1.2 million in restitution to the New York State Tax Commission. ``They admitted to having nuclear capability and weapons at this moment,'' said Rep. Curt Weldon, who headed a delegation of U.S. lawmakers that visited [meettransport] Pyongyang for three days ending Sunday. Blasphemy is punishable by death [die execute] under the Pakistan Penal Code. We discussed [phone-write meet] the Middle East peace process.

Event Trigger Classification Errors

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Scene understanding:This was the Italian ship that was taken -- that was captured by Palestinian terrorists back in 1985 [die_time] and some may remember the story of Leon clinghover, he was in a cheal chair and the terrorists shot him and pushed him over the side of the ship into the Mediterranean [die_place] where he [die_victim] obviously, died.She [die_victim] was going to fight to the death. Then police say the baby's mother pulled out a kitchen knife [die_instrument] opinion on the 911 tape you can hear Williams tape say "go ahead kill me." Coreference:another story out of Belgrade [attack_place], violence at the highest form. Unusual syntactic structure:Two f-14 Tomcats struck the targets, the same area was a site [attack_place] of heavy bombing yesterday. The EU foreign ministers met hours after U.S. President George W. Bush gave Saddam [attack_target] 48 hours to leave Iraq or face invasion.

Event Argument Identification Missing Errors

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OOV:We've seen in the past in Bosnia for example, you held elections and all of the old ethnic thugs [election_person] get into power because they have organization and they have money and they stop the process of genuine building of democracy.There are charges, U.S. charges which have expired but could, I am told, possibly be re -- restarted for piracy, hostage taking and conspiracy [charge_crime]. Stewart and former imclone CEO Sam Waksal shared a broker who now also faces charges of obstruction of justice and perjury [charge_crime]. I was born four years too late to have slept with JFK [born_time]?He called the case and I'm quoting now, a judge's worst nightmare, but he noted that Maryland Parole Boards and the facility where Michael Serious was held, the institution made what the judge called the final decision on whether to release serious [release-parole_person]. Last week Williamson, a mother of four, was found stabbed to death at a condominium [die_place] in Greenbelt, Maryland. A source tell US Enron is considering suing its own investment bankers for giving it bad financial advice [Sue_crime].

Event Argument Identification Missing Errors (Cont’)

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He's been in Libya and he's been living under the protection of Saddam Hussein in Baghdad [die_place], but he is wanted for murder in Italy Italy. The EU foreign ministers met hours after U.S. President George W. Bush [meet_entity] gave Saddam 48 hours to leave Iraq or face invasion.

Event Argument Identification Spurious Errors

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His private plane [vehicle artifact] arrived at Heathrow Airport.a cruise ship [instrument target] is being searched off the Hawaii coast after two notes threatening terrorist attack were found on board.

Event Argument Role Classification Errors

Why Trigger Labeling is so Hard? DT this “this is the largest pro-troops demonstration that has ever

been in San Francisco” RP forward “We've had an absolutely terrific story, pushing forward

north toward Baghdad” WP what “what happened in” RB back “his men back to their compound” IN over “his tenure at the United Nations is over” IN out “the state department is ordering all non-essential diplomats” CD nine eleven “nine eleven” RB formerly “McCarthy was formerly a top civil servant at”

Why Trigger Labeling is so Hard? A suicide bomber detonated explosives at the

entrance to a crowded medical teams carting away dozens of

wounded victims dozens of Israeli tanks advanced into

thenorthern Gaza Strip Many nouns such as “death”, “deaths”, “blast”,

“injuries” are missing

Why Argument Labeling is so Hard? Two 13-year-old children were among those killed in the Haifa

bus bombing, Israeli public radio said, adding that most of the victims were youngsters

Israeli forces staged a bloody raid into a refugee camp in central Gaza targeting a founding member of Hamas

Israel's night-time raid in Gaza involving around 40 tanks and armoured vehicles

Eight people, including a pregnant woman and a 13-year-old child were killed in Monday's Gaza raid

At least 19 people were killed and 114 people were wounded in Tuesday's southern Philippines airport

The waiting shed literally exploded

Wikipedia “A shed is typically a simple, single-storey structure in a back garden or on an allotment that is used for storage, hobbies, or as a workshop."

Why Argument Labeling is so Hard? Two 13-year-old children were among those killed in the Haifa

bus bombing, Israeli public radio said, adding that most of the victims were youngsters

Fifteen people were killed and more than 30 wounded Wednesday as a suicide bomber blew himself up on a student bus in the northern town of Haifa

Two 13-year-old children were among those killed in the Haifa bus bombing

State-of-the-art and Remaining Challenges State-of-the-art Performance (F-score)

English: Trigger 70%, Argument 45% Chinese: Trigger 68%, Argument 52% Single human annotator: Trigger 72%, Argument 62%

Remaining Challenges Trigger Identification

Generic verbs Support verbs such as “take” and “get” which can only represent an event mention together with

other verbs or nouns Nouns and adjectives based triggers

Trigger Classification “named” represents a “Personnel_Nominate” or “Personnel_Start-Position”? “hacked to death” represents a “Life_Die” or “Conflict_Attack”?

Argument Identification Capture long contexts

Argument Classification Capture long contexts Temporal roles

(Ji, 2009; Li et al., 2011)

IE

Information Networks

Authors VenuesTextsTime/Location/

Cost Constraints

IE in Rich Contexts

Human Collaborative Learning

Capture Information Redundancy• When the data grows beyond some certain size, IE task is

naturally embedded in rich contexts; the extracted facts become inter-dependent

• Leverage Information Redundancy from:• Large Scale Data (Chen and Ji, 2011)• Background Knowledge (Chan and Roth, 2010; Rahman and Ng, 2011)• Inter-connected facts (Li and Ji, 2011; Li et al., 2011; e.g. Roth and Yih, 2004;

Gupta and Ji, 2009; Liao and Grishman, 2010; Hong et al., 2011)• Diverse Documents (Downey et al., 2005; Yangarber, 2006; Patwardhan and

Riloff, 2009; Mann, 2007; Ji and Grishman, 2008)• Diverse Systems (Tamang and Ji, 2011)• Diverse Languages (Snover et al., 2011)• Diverse Data Modalities (text, image, speech, video…)

• But how? Such knowledge might be overwhelming…

Cross-Sent/Cross-Doc Event Inference Architecture

TestDoc

TestDoc

Within-SentEventTagger

Cross-DocInference

CandidateEvents &

Confidence

RefinedEvents

Within-SentEventTagger

Cross-SentInference

Cross-SentInference

RelatedEvents &

Confidence

UMASSINDRI

IR

Cluster of Related

Docs

Cluster of Related

Docs

Baseline Within-Sentence Event Extraction

1. Pattern matching• Build a pattern from each ACE training example of an event

• British and US forces reported gains in the advance on Baghdad PER report gain in advance on LOC

2. MaxEnt models① Trigger Classifier

• to distinguish event instances from non-events, to classify event instances by type

② Argument Classifier• to distinguish arguments from non-arguments

③ Role Classifier• to classify arguments by argument role

④ Reportable-Event Classifier• to determine whether there is a reportable event instance

Global Confidence Estimation

Within-Sentence IE system produces local confidence

IR engine returns a cluster of related docs for each test doc

Document-wide and Cluster-wide Confidence• Frequency weighted by local confidence• XDoc-Trigger-Freq(trigger, etype): The weighted frequency of string

trigger appearing as the trigger of an event of type etype across all related documents

• XDoc-Arg-Freq(arg, etype): The weighted frequency of arg appearing as an argument of an event of type etype across all related documents

• XDoc-Role-Freq(arg, etype, role): The weighted frequency of arg appearing as an argument of an event of type etype with role role across all related documents

• Margin between the most frequent value and the second most frequent value, applied to resolve classification ambiguities

• ……

Cross-Sent/Cross-Doc Event Inference ProcedureRemove triggers and argument annotations with local or cross-doc

confidence lower than thresholds• Local-Remove: Remove annotations with low local confidence• XDoc-Remove: Remove annotations with low cross-doc confidence

Adjust trigger and argument identification and classification to achieve document-wide and cluster-wide consistency• XSent-Iden/XDoc-Iden: If the highest frequency is larger than a threshold,

propagate the most frequent type to all unlabeled candidates with the same strings

• XSent-Class/XDoc-Class: If the margin value is higher than a threshold, propagate the most frequent type and role to replace

low-confidence annotations

Experiments: Data and Setting

Within-Sentence baseline IE trained from 500 English ACE05 texts (from March – May of 2003)

Use 10 ACE05 newswire texts as development set to optimize the global confidence thresholds and apply them for blind test

Blind test on 40 ACE05 texts, for each test text, retrieved 25 related texts from TDT5 corpus (278,108 texts, from April-Sept. of 2003)

Selecting Trigger Confidence Thresholdsto optimize Event Identification F-measure on Dev Set

Best F=64.5%

69.8% 69.8%

73.8%

Selecting Argument Confidence Thresholds to optimize Argument Labeling F-measure on Dev Set

F=42.3%43.7%

48.0% 48.2%48.3%

51.2%

Experiments: Trigger Labeling

PerformanceSystem/Human

Precision Recall F-Measure

Within-Sent IE (Baseline) 67.6 53.5 59.7

After Cross-Sent Inference 64.3 59.4 61.8

After Cross-Doc Inference 60.2 76.4 67.3

Human Annotator 1 59.2 59.4 59.3

Human Annotator 2 69.2 75.0 72.0

Inter-Adjudicator Agreement 83.2 74.8 78.8

Experiments: Argument Labeling

Performance

System/Human

Argument Identification

ArgumentClassification

Accuracy

Argument Identification

+Classification

P R F P R F

Within-Sent IE 47.8 38.3 42.5 86.0 41.2 32.9 36.3

After Cross-Sent Inference

54.6 38.5 45.1 90.2 49.2 34.7 40.7

After Cross-Doc Inference

55.7 39.5 46.2 92.1 51.3 36.4 42.6

Human Annotator 1 60.0 69.4 64.4 85.8 51.6 59.5 55.3

Human Annotator 2 62.7 85.4 72.3 86.3 54.1 73.7 62.4

Inter-Adjudicator Agreement

72.2 71.4 71.8 91.8 66.3 65.6 65.9

Global Knowledge based Inference for Event Extraction

Cross-document inference (Ji and Grishman, 2008)

Cross-event inference (Liao and Grishman, 2010)

Cross-entity inference (Hong et al., 2011)

All-together (Li et al., 2011)

Within a cluster of topically-related documents, the distribution is much more convergent; closer to its distribution in the collection of topically related documents than the uniform training corpora

e.g. In the overall information networks only 7% of “fire” indicate “End-Position” events; while all of “fire” in a topic cluster are “End-Position” events

e.g. “Putin” appeared as different roles, including “meeting/entity”, “movement/person”, “transaction/recipient” and “election/person”, but only played as an “election/person” in one topic cluster

Topic Modeling can enhance information network construction by grouping similar objects, event types and roles together

Leveraging Redundancy with Topic Modeling

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Bootstrapping Event Extraction

• Both systems rely on expensive human labeled data, thus suffers from data scarcity (much more expensive than other NLP tasks due to the extra tagging tasks of entities and temporal expressions)

Questions:

• Can the monolingual system benefit from bootstrapping techniques with a relative small set of training data?

• Can a monolingual system (in our case, the Chinese event extraction system) benefit from the other resource-rich monolingual system (English system)?

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Cross-lingual Co-Training

Intuition: The same event has different “views” described in

different languages, because the lexical unit, the grammar and sentence construction differ from one language to the other.

Satisfy the sufficiency assumption

Cross-lingual Co-Training for Event Extraction

Unlabeled Bitexts

Labeled Samplesin Language A

Labeled Samplesin Language B

train

System for Language A

System for Language B

train

Projected Samples A

Cross-lingualProjection

Projected Samples B

High Confidence Samples A

High Confidence Samples B

Event ExtractionEvent ExtractionBilingual Pool with

constant size

Select at Random

A

B

(Chen and Ji, 2009)

Bootstrapping: n=1: trust yourself and teach yourself Co-training: n=2 (Blum and Mitchell,1998)

• the two views are individually sufficient for classification

• the two views are conditionally independent given the class

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Cross-lingual Projection

• A key operation in the cross-lingual co-training algorithm• In our case, project the triggers and the arguments from one language into

the other language according to the alignment information provided by bitexts.

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Experiments (Chen and Ji, 2009)

Data • ACE 2005 corpus

• 560 English documents • 633 Chinese documents

• LDC Chinese Treebank English Parallel corpus • 159 bitexts with manual alignment

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Experiment results

Self-training, and Co-training (English- labeled & Combined-labeled)

for Trigger Labeling

Self-training, and Co-training (English- labeled & Combined-labeled)

for Argument Labeling

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Analysis

• Self-training: a little gain of 0.4% above the baseline for trigger labeling and a loss of 0.1% below the baseline for argument labeling. The deterioration tendency of the self-training curve indicates that entity extraction errors do have counteractive impacts on argument labeling.

• Trust-English method: a gain of 1.7% for trigger labeling and 0.7% for argument labeling.

• Combination method: a gain of 3.1% for trigger labeling and 2.1% for argument labeling. The third method outperforms the second method.

5. The explosion comes a month after

6. a bomb exploded at a McDonald's restaurant in Istanbul, causing damage but no injuries

1. An explosion in a cafe at one of the capital's busiest intersections killed one woman and injured another Tuesday

2. Police were investigating the cause of the explosion in the restroom of the multistory Crocodile Cafe in the commercial district of Kizilay during the morning rush hour

Event Coreference Resolution: Task

3. The blast shattered walls and windows in the building

4. Ankara police chief Ercument Yilmaz visited the site of the morning blast

7. Radical leftist, Kurdish and Islamic groups are active in the country and have carried out the bombing in the past

Category Feature Description

Event type type_subtype pair of event type and subtype

Trigger trigger_pair trigger pairs

pos_pair part-of-speech pair of triggers

nominal if the trigger of EM2 is nominal

exact_match if the triggers exactly match

stem_match if the stems of triggers match

trigger_sim trigger similarity based on WordNet

Distance token_dist the number of tokens between triggers

sentence_dist the number of sentences between event mentions

event_dist the number of event mentions between EM1 and EM2

Argument overlap_arg the number of arguments with entity and role match

unique_arg the number of arguments only in one event mention

diffrole_arg The number of coreferential arguments but role mismatch

Typical Event Mention Pair Classification Features

Incorporating Event Attribute as FeaturesEvent

AttributesEvent Mentions Attribute

Value

ModalityToyota Motor Corp. said Tuesday it will promote Akio Toyoda, a grandson of the company's founder who is widely viewed as a candidate to some day head Japan's largest automaker.

Other

Managing director Toyoda, 46, grandson of Kiichiro Toyoda and the eldest son of Toyota honorary chairman Shoichiro Toyoda, became one of 14 senior managing directors under a streamlined management system set to be…

Asserted

Polarity At least 19 people were killed in the first blast Positive

There were no reports of deaths in the blast Negative

Genericity

An explosion in a cafe at one of the capital's busiest intersections killed one woman and injured another Tuesday

Specific

Roh has said any pre-emptive strike against the North's nuclear facilities could prove disastrous

Generic

Tense Israel holds the Palestinian leader responsible for the latest violence, even though the recent attacks were carried out by Islamic militants

Past

We are warning Israel not to exploit this war against Iraq to carry out more attacks against the Palestinian people in the Gaza Strip and destroy the Palestinian Authority and the peace process.

Future

Attribute values as features: Whether the attributes of an event mention and its candidate antecedent event conflict or not; 6% absolute gain (Chen et al., 2009)

Clustering Method 1: Agglomerative Clustering

Basic idea:

Start with singleton event mentions, sort them according to the occurrence in the document

Traverse through each event mention (from left to right), iteratively merge the active event mention into a prior event (largest probability higher than some threshold) or start the event mention as a new event

Clustering Method 2: Spectral Graph ClusteringTrigger explosion

Arguments Role = Place

a cafe

Role = Time

Tuesday

Trigger explosion

Arguments Role = Place

restroom

Role = Time

morning rush

hourTrigger explosion

Arguments Role = Place

building

Trigger blast

Arguments Role = Place

site

Role = Time

morningTrigger explosion

Arguments Role = Time

a monthafter

Trigger exploded

Arguments Role = Place

restaurant

Trigger bombing

Arguments Role = Attacker

groups

(Chen and Ji, 2009)

Spectral Graph Clustering0.8

0.7

0.90.9 0.6 0.8

0.8

0.7

0.1

0.2

0.3

0.2

A

B

cut(A,B) = 0.1+0.2+0.2+0.3=0.8

0.3

Spectral Graph Clustering (Cont’)

• Start with full connected graph, each edge is weighted by the coreference value

• Optimize the normalized-cut criterion (Shi and Malik, 2000)

• vol(A): The total weight of the edges from group A• Maximize weight of within-group coreference links• Minimize weight of between-group coreference links

( , ) ( , )min ( , )

( ) ( )

cut A B cut A BNCut A B

vol A vol B

State-of-the-art Performance

MUC metric does not prefer clustering results with many singleton event mentions (Chen and Ji, 2009)

Remaining Challenges

The performance bottleneck of event coreference resolution comes from the poor performance of event mention labeling

Beyond ACE Event Coreference

Annotate events beyond ACE coreference definition• ACE does not identify Events as coreferents when one

mention refers only to a part of the other• In ACE, the plural event mention is not coreferent with

mentions of the component individual events.• ACE does not annotate:

“Three people have been convicted…Smith and Jones were found guilty of selling guns…”

“The gunman shot Smith and his son. ..The attack against Smith.”

CMU Event Coref Corpus• Annotate related events at the document level, including

subevents.

Examples:• “drug war” (contains subevents: attacks, crackdowns,

bullying…) • “attacks” (contains subevents: deaths, kidnappings,

assassination, bombed…)

Applications• Complex Question Answering

• Event questions: Describe the drug war events in Latin America. • List questions: List the events related to attacks in the drug war. • Relationship questions: Who is attacking who?

Drug War eventsWe don't know who is winning the drug war in Latin America, but we know who's losing it -- the press. Over the past six months, six journalists have been killed and 10 kidnapped by drug traffickers or leftist guerrillas -- who often are one and the same -- in Colombia. Over the past 12 years, at least 40 journalists have died there. The attacks have intensified since the Colombian government began cracking down on the traffickers in August, trying to prevent their takeover of the country.

drug war (contains subevents: attacks, crackdowns, bullying …) lexical anchor:drug warcrackdown lexical anchor: cracking down arguments: Colombian government, traffickers, Augustattacks (contains subevents: deaths, kidnappings, assassination, bombed..) attacks (set of attacks) lexical anchor: attacks arguments: (inferred) traffickers, journalists

Events to annotate• Events that happened

“Britain bombed Iraq last night.”

• Events which did not happen “Hall did not speak about the bombings.”

• Planned events planned, expected to happen, agree to do…

“Hall planned to meet with Saddam.”

Other cases

• Event that is pre-supposed to have happenedStealing event

“It may well be that theft will become a bigger problem.”

• Habitual in present tense“It opens at 8am.”

Annotating related entities

• In addition to event coreference, we also annotate entity relations between events. e.g. Agents of bombing events may be related via an “ally”

relation.

e.g. “the four countries cited, Colombia, Cuba, Panama and Nicaragua, are not only where the press is under greatest attack …”

Four locations of attack are annotated and the political relation (CCPN) is linked.

Other FeaturesArguments of events• Annotated events may have arguments.• Arguments (agent, patient, location, etc.) are also

annotated.

Each instance of the same event type is assigned a unique id.e.g. attacking-1, attacking-2

Annotating multiple intersecting meaning layers

Three types of annotations have been added with the GATE tool

• What events are related? Which events are subevents of what events? (Event Coreference)

• What type of relationships between entities? (Entity Relations)

• How certain are these events to have occurred? (Committed Belief )

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Coarse-grained predicate-argument representations defined in Propbank (Palmer et al., 2005, Xue and Palmer, 2009) and FrameNet (Baker et al., 1998)

No attempt to cluster the predicatesAssign coarse-grained roles to arguments

Fine-grained event trigger and argument representations defined in ACE and EREOnly covers 33 subtypes; e.g., Some typical types of emergent events such as “donation” and “evacuation” in response to a natural disaster are missing

Both representations are missing:Event hierarchies, Relations among eventsMeasurement to quantify uncertainty, Implicit argument rolesThe narrator’s role, profile and behavior intent and temporal effectsHard to construct a timeline of events across documentsEfforts are being made by the DEFT event working group (NAACL13/ACL14 Event Workshops and this DEFT PI meeting Event Workshop)

Limitations of Previous Event Representations

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Coarse-grained predicate-argument representations defined in Propbank (Palmer et al., 2005, Xue and Palmer, 2009) and FrameNet (Baker et al., 1998)

No attempt to cluster the predicatesAssign coarse-grained roles to arguments

Fine-grained event trigger and argument representations defined in ACE and EREOnly covers 33 subtypes; e.g., Some typical types of emergent events such as “donation” and “evacuation” in response to a natural disaster are missing

Both representations are missing:Event hierarchies, Relations among eventsMeasurement to quantify uncertainty, Implicit argument rolesThe narrator’s role, profile and behavior intent and temporal effectsHard to construct a timeline of events across documentsEfforts are being made by the DEFT event working group (NAACL13/ACL14 Event Workshops and this DEFT PI meeting Event Workshop)

Limitations of Previous Event Representations

Event

Taking non-routine actions

Planning and Organizing

Resolution

Timeline

Sensing environment to identify precursor events

Behavioral Response

Organizing ActivitiesTaking Actions

Event Conclusion

Specific Characteristics of Emergent Events

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Process of Behavioral Responses to Emerging Events

Obtain, Understand, Trust,

Personalize actionable information

Seek/Obtain confirmation

Take action

Diffuse contradictory information,

discredit trusted sources

Discredit trusted sources, block

information flow

Disturb actions

(Tyshchuk et al., 2014)

A New Representation for Events

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Current NLP’s Focus

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An Example: Input

[Oct.25 News]WNYC: The Office of Emergency Management situation room is now open, and Mayor Michael Bloomberg said they are monitoring the progress of the storm. "We saw that hurricanes like Irene can really do damage and we have to take them seriously, but we don't expect based on current forecasts to have anything like that," Bloomberg said. "But we're going to make sure we're prepared." He advised residents in flood-prone areas be prepared to evacuate.[Oct.29 Tweets]OMG!!! NYC IS GETTING THE EYE OF HURRICANE SANDY NEXT WEEK....SCARY!!! I HAVE TO EVACUATE MY NEIGHBORHOOD!

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An Example: Output

4-tuple Temporal Representation (Ji et al., 2011)

Challenges:Capture incomplete informationAccommodate uncertaintyAccommodate different granularities

Solution:express constraints on start and end times for slot value4-tuple <t1, t2, t3, t4>: t1 < tstart < t2 t3 < tend < t4

Document text (2001-01-01) T1 T2 T3 T4Chairman Smith -infinite 20010101 20010101 +infinite

Smith, who has been chairman for two years

-infinite 19990101 20010101 +infinite

Smith, who was named chairman two years ago

19990101 19990101 19990101 +infinite

Smith, who resigned last October -infinite 20001001 20001001 20001031

Smith served as chairman for 7 years before leaving in 1991

19840101 19841231 19910101 19911231

Smith was named chairman in 1980

19800101 19801231 19800101 +infinite

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70

A number of recent event extraction programs such as ACE identify several common types of events

Defining and identifying those types rely heavily on expert knowledgeReaching an agreement among the experts or annotators may require extensive human labor

Address the issue of portability – How can we automatically detect novel event types? General Approach

Follow social science theories (Tyshchuk et al., 2013) to discover salient emergent event typesDiscover candidate event types based on event trigger clustering via paragraph discovery methods (Li et al., 2010)Rank these clusters based on their salience and novelty in the target unlabeled corpus

Open Domain Event Type Discovery

Event Mention Extraction

Texts

Name/Nominal/TimeMentionExtraction

CoreferenceResolution

RelationExtraction

EventExtraction

Cross-docEntityClustering/Linking

100％

• Errors are compounded from stage to stage• No interaction between individual predictions• Incapable of dealing with global dependencies

Slot Filling

PERFORMANCE CEILING

90％ 70％ 60％ 50％ 40％

KB

• Traditional Pipelined Approach:

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General Solutions

Joint Inference Joint Modeling

Model 1

Prediction

Inference

Prediction

Model 2

Model n

… Task1

Task2

Taskn

…

• Constrained Conditional Models, ILP [Roth2004,Punyakanok2005,Roth2007, Chang2012, Yang2013]

• Re-ranking [Ji2005,McClosky2011]• Dual decomposition [Rush2010]

• Probabilistic Graphical Models[Sutton2004,Wick2012,Singh2013]

• Markov logic networks [Poon2007,Poon2010,Kiddon2012]

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Joint Modeling with Structured Prediction

• One Single Uniformed Model to Extract All (Li et al., 2013; Li and Ji, 2014)

• Avoid error compounding

• Local predictions can be mutually improved

• Arbitrary global features can be automatically learnedselectively from the entire structure with lost cost

In Baghdad, a cameraman died when an American tank fired on the Palestine Hotel.

place

placevictim

target

targetinstrumentinstrument

LOC

Die Attack O O O O O O O O O O O O

PER VEH FAC

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Event Mention Extraction Results

Trigger Argument30

35

40

45

50

55

60

65

70

7568.3

48.3

59.7

36.5

65.9

43.9

65.7

46.5

67.5

52.7

Cross-entity in Hong et. al. 2011Sentence-level in Hong et. al. 2011Pipelined MaxEnt classi-fiersJoint w/ local featuresJoint w/ local + global features

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Our Proposed Event Relation Taxonomy

• Focus: subevent, confirmation, causality and temporality

Inheritance

Expansion

Comparison

Contingency

Temporality

ReemergenceSubeventVariation

ConjunctionDisjunctionConfirmationCompetitionNegationOppositeConcession

CausalityConditionality

Synchronism

Reference/TargetAncestor/DescendantSemina/Variance

Generation/NeighborshipGeneration/NeighborshipGeneration/Instantiation

Superior/Inferior/parallelismInitiator/NegatorN/APrerequisite/Opposite to ExpectationCause/ResultCondition/Emergence

Priority/PosteriorityN/A

Main Type Subtype Role

Asynchronism

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Event Relation: Inheritance

InheritanceReemergenceSubeventVariation

Reference/TargetAncestor/DescendantSemina/Variance

Eruption of Mount Vesuvius in 1944.

Eruption of Mount Vesuvius in 1906.

Inheritance.Reemergence

Inheritance.Variation

Mount Vesuvius keeps silent recently.

Inheritance.Subevent

The eruption covered most of north area

with ash.

Definition: if X clones or succeeds Y, or serves as a revolutionary change of Y

Role=Reference Role=Descendant Role=Variance 76

Event Relation: Expansion

Definition: if X and Y jointly constitute a larger event or share the same subevent, or X serves as the fine-grain instance or evidence of Y,

ExpansionConjunctionDisjunctionConfirmation

Generation/NeighborshipGeneration/NeighborshipGeneration/Instantiation

Second Explosion. First Explosion.

Boston Marathon Bombing.

Expansion.Conjunction

Expansion.Disjunction

Arrest the suspect

Try the suspect

Dzhokhar was suspected

Made bombs at home.

Appear on the scene.

Expansion.Confirmation

X and Y share the same subevent

X and Y jointly constitute a main event

X serves as the fine-grain instance or evidence of Y 77

Event Relation: Contingency

Definition: if X creates a condition for the emergence of Y, or results in Y

The operation to raise the Kursk submarine was scheduled to begin in about two weeks.

The special hoisting equipment had been properly installed in the massive pick-up boat.

Contingency.ConditionalityX creates a condition for the emergence of Y

Contingency CausalityConditionality

Cause/ResultCondition/Emergence

Role=Condition Role=Emergence

A violent storm would hit Barents sea.

Salvage plan was postponed indefinitely.

Contingency.CausalityX results in the emergence of Y

Role=Cause

Role=Result 78

Primacy Effect

• Relations: BEFORE, AFTER, INCLUDES, INCLUDED_IN, SIMULTANEOUS, VAGUE

• Annotators must label all pairs within one sentence window• Annotation guidelines address resulting difficult cases• Evaluate and develop systems to decide whether a pair can be

related 79

There were four or five people inside, and they just started firing

Ms. Sanders was hit several times and was pronounced dead at the scene.

The other customers fled, and the police said it did not appear that anyone else was injured.

There were four or five people inside, and they just started firing

Ms. Sanders was hit several times and was pronounced dead at the scene.

The other customers fled, and the police said it did not appear that anyone else was injured.

Original TimeBank** TimeBank-Dense

(Cassidy et al., 2014); ** (Pustejovsky et al., 2003)

From TimeBank to TimeBank-Dense New relation

Event Relation: Temporality

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Main ChallengesFine-grained distinction / Implicit logic relations (Hong et al., 2012)The text order by itself is a poor predictor of temporal order (3% correlation) (Ji et al., 2009)

Deep background and commonsense knowledge acquisitionFrameNet/Google ngram / Concept Net /Background news

Retrospective Historical Event Detection precursor prediction

Take advantage of rich event representation and Abstract Meaning Representation (Banarescu et al., 2013)

Temporal Event Tracking (Ji et al., 2010) and Temporal Slot Filling (Ji et al., 2013; Cassidy and Ji, 2014)

Apply Structured prediction to capture long syntactic contextsExploit global knowledge from related events and Wikipedia to conduct temporal reasoning and predict implicit time arguments

Event Relation Extraction Approach

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Representing Event-Event Relations in KB

Entity KB

ID = E1 Name = Office of Emergency Management

ID = E2 Name = Michael Bloomberg Title = Mayor Employer = E5

ID = E3 Name = Residents in flood-phone areas

ID = E4 Name = WNYC Property = News

ID = E5 Name = New York City

ID = E6 Name = Tammi Delancy

#Follower s= 211

#Friends = 770

Role = Participant &Commenter

City_of_residence = E5

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Representing Event-Event Relations in KB

Event KB

ID = EV1

Properties Type=Warning

Novelty=1.0

Modality = Asserted

Tense = Past

Polarity = Positive

Genericity = Specific

Trigger advised

Arguments Advisor = E1, E2

Advisees = E3

Advice = Evacuation

Narrator = E4 Time = 10/25/2012 Place = E5

Result Event EV2

Children Event EV

ID = EV2

Properties Type=Evacuation

Novelty=1.0

Modality = Asserted

Tense= Future

Polarity = Positive

Genericity = Specific

Trigger evacuate

Arguments Narrator = E4 Time = 10/29/2012 Place = E5

Cause Event EV1

Parent Event EV4

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We have a reasonable understanding on how to detect temporal relations (Ji et al., 2013; Cassidy and Ji, 2014) but not othersMain Challenges

Clustering coreferential events - what is event coreference anyway (Hovy et al., 2013)?Event-event relations are often logic relations without explicit linguistic indicatorsFine-grained distinction / Implicit logic relations (Hong et al., 2012)

Deep background and commonsense knowledge acquisitionFrameNet/Google ngram / Concept Net /Background newsRetrospective Historical Event Detection precursor prediction (Hong and Ji, 2014submission)Take advantage of rich knowledge representation such as AMR (Banarescu et al., 2013)

Pilot System