computing textual inferences cleo condoravdi palo alto research center georgetown university...
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Computing Textual InferencesComputing Textual Inferences
Cleo Condoravdi
Palo Alto Research Center
Georgetown University
Halloween, 2008
OverviewOverviewMotivation
Local Textual Inference Textual Inference Initiatives and refinements
PARC’s BRIDGE systemXLE Abstract Knowledge Representation (AKR)
Conceptual and temporal structureContextual structure and instantiability
Semantic relationsEntailments and presuppositionsRelative polarity
Entailment and Contradiction (ECD)
(Interaction with external temporal reasoner)
Access to content: existential claimsAccess to content: existential claimsWhat happened? Who did what to whom?What happened? Who did what to whom?
Microsoft managed to buy Powerset.
Microsoft acquired Powerset.
Shackleton failed to get to the South Pole.
Shackleton did not reach the South Pole.
The destruction of the file was not illegal.
The file was destroyed.
The destruction of the file was averted.
The file was not destroyed.
Access to content: monotonicityAccess to content: monotonicityWhat happened? Who did what to whom?What happened? Who did what to whom?
Every boy managed to buy a small toy.
Every small boy acquired a toy.
Every explorer failed to get to the South Pole.
No experienced explorer reached the South Pole.
No file was destroyed.
No sensitive file was destroyed.
The destruction of a sensitive file was averted.
A file was not destroyed.
Access to content: temporal domainAccess to content: temporal domainWhat happened when? What happened when?
Ed visited us every day last week.
Ed visited us on Monday last week.
Ed has been living in Athens for 3 years.
Mary visited Athens in the last 2 years.
Mary visited Athens while Ed lived in Athens.
The deal lasted through August, until just before the government took over Freddie. (NYT, Oct. 5, 2008)
The government took over Freddie after August.
Grammatical analysis for access to Grammatical analysis for access to contentcontent
Identify “Microsoft” as the buyer argument of the verb “buy”Identify “Shackleton” as the traveler argument of the verb “get to”
Identify lexical relation between “destroy” and “destruction”Identify syntactic relation between verbal predication “destroy the file” and
nominal predication “destruction of the file”
Identify the infinitival clause as an argument of “manage” and “fail”
Identify the noun phrases “every”, “a”, “no” combine with
Identify the phrases “every day”, “on Monday”, “last week” as modifiers of “visit”
Identify “has been living” as a present progressive
Knowledge about words for access to Knowledge about words for access to contentcontent
The verb “acquire” is a hypernym of the verb “buy”The verbs “get to” and “reach” are synonyms
Inferential properties of “manage”, “fail”, “avert”, “not”
Monotonicity properties of “every”, “a”, “no”, “not”
Restrictive behavior of adjectival modifiers “small”, “experienced”, “sensitive”
The type of temporal modifiers associated with prepositional phrases headed by “in”, “for”, “on”, or even nothing (e.g. “last week”, “every day”)
Toward NL UnderstandingToward NL Understanding
Local Textual Inference A measure of understanding a text is the ability to make
inferences based on the information conveyed by it. We can test understanding by asking questions about the text.
Veridicality reasoningDid an event mentioned in the text actually occur?
Temporal reasoningWhen did an event happen? How are events ordered in time?
Spatial reasoningWhere are entities located and along which paths do they
move?
Causality reasoning Enablement, causation, prevention relations between events
Local Textual Inference Local Textual Inference
PASCAL RTE Challenge (Ido Dagan, Oren Glickman) 2005, 2006
PREMISE
CONCLUSIONTRUE/FALSE
Rome is in Lazio province and Naples is in Campania.
Rome is located in Lazio province.
TRUE ( = entailed by the premise)
Romano Prodi will meet the US President George Bush in his capacity as the president of the European commission.
George Bush is the president of the European commission.
FALSE (= not entailed by the premise)
PARC Entailment and Contradiction PARC Entailment and Contradiction Detection (ECD)Detection (ECD)
Text: Kim hopped.Hypothesis: Someone moved.Answer: TRUE
Text: Sandy touched Kim.Hypothesis: Sandy kissed Kim.Answer: UNKNOWN
Text: Sandy kissed Kim.Hypothesis: No one touched Kim.Answer: NO
Text: Sandy didn’t wait to kiss Kim.Hypothesis: Sandy kissed Kim.Answer: AMBIGUOUS
Linguistic meaning vs. speaker meaningLinguistic meaning vs. speaker meaning
Not a pre-theoretic but rather a theory-dependent distinction Multiple readings
ambiguity of meaning?single meaning plus pragmatic factors?
The diplomat talked to most victimsThe diplomat did not talk to all victimsUNKNOWN / YES
You can have the cake or the fruit.
You can have the fruit
I don’t know which.
YESUNKNOWN
World Knowledge World Knowledge
Romano Prodi will meet the US President George Bush in his capacity as the president of the European commission.
George Bush is the president of the European commission.
FALSE (= not entailed by the premise on the correct anaphoric resolution)
G. Karas will meet F. Rakas in his capacity as the president of the European commission.
F. Rakas is the president of the European commission.
TRUE (= entailed by the premise on one anaphoric resolution)
Recognizing textual entailmentsRecognizing textual entailments
Monotonicity Calculus, Polarity, Semantic RelationsMuch of language-oriented reasoning is tied to specific
words, word classes and grammatical featuresClass 1: “fail”, “refuse”, “not”, …Class 2: “manage”, “succeed”, …Tenses, progressive –ing form, …
Representation and inferential properties of modifiers of different kinds
throughout July vs. in July
for the last three years vs. in the last three years sleep three hours -- duration sleep three times -- cardinality
XLE PipelineXLE Pipeline
• Mostly symbolic system• Ambiguity-enabled through packed representation of analyses• Filtering of dispreferred/improbable analyses is possible
• OT marks• mostly on c-/f-structure pairs, but also on c-structures• on semantic representations for selectional preferences
• Statistical models• PCFG-based pruning of the chart of possible c-structures• Log-linear model that selects n-best c-/f-structure pairs
morphological analyses
c-structures
c-/f-structure pairs
CSTRUCTURE OT marks PCFG-based chart pruning
“general” OT markslog-linear model
Ambiguity is rampant in languageAmbiguity is rampant in language
Alternatives multiply within and across layers…
C-structure
F-structure
Linguistic S
em
Abstract K
R
KR
R
What not to doWhat not to do
Use heuristics to prune as soon as possible
C-structure
F-structure
Linguistic sem
Abstract K
R
KR
R
XX
X
Statistics
X
Oops: Strong constraints may reject the so-far-best (= only) option
Fast computation, wrong result
X
Manage ambiguity insteadManage ambiguity instead
The sheep liked the fish.How many sheep?
How many fish?
The sheep-sg liked the fish-sg.The sheep-pl liked the fish-sg.The sheep-sg liked the fish-pl.The sheep-pl liked the fish-pl.
Options multiplied out
The sheep liked the fish sgpl
sgpl
Options packed
Packed representation:– Encodes all dependencies without loss of information– Common items represented, computed once– Key to practical efficiency with broad-coverage grammars
System OverviewSystem Overview
“A girl hopped.”
stringsyntactic F-structure
LFGParser
rewrite rules
AKR (Abstract Knowledge Representation)
XLE PipelineXLE Pipeline
Process OutputText-Breaking Delimited Sentences
NE recognition Type-marked Entities (names, dates, etc.)
Morphological Analysis Word stems + features
LFG parsing Functional Representation
Semantic Processing Scope, Predicate-argument structure
AKR Rules Abstract Knowledge Representation
Alignment Aligned T-H Concepts and Contexts
Entailment and Contradiction Detection
YES / NO / UNKNOWN
XLE System ArchitectureXLE System ArchitectureText Text AKR AKR
Parse text to f-structuresConstituent structure
Represent syntactic/semantic features (e.g. tense, number)
Localize arguments (e.g. long-distance dependencies, control)
Rewrite f-structures to AKR clauses
Collapse syntactic alternations (e.g. active-passive)
Flatten embedded linguistic structure to clausal form
Map to concepts and roles in some ontology
Represent intensionality, scope, temporal relations
Capture commitments of existence/occurrence
AKR representationAKR representation
concept term WordNet synsets
thematicrole
A collection of statements
instantiability facts
event time
F-structures F-structures vs.vs. AKR AKR
Nested structure of f-structures vs. flat AKRF-structures make syntactically, rather than conceptually, motivated
distinctions Syntactic distinctions canonicalized away in AKR
Verbal predications and the corresponding nominalizations or deverbal adjectives with no essential meaning differences
Arguments and adjuncts map to roles
Distinctions of semantic importance are not encoded in f-structures Word sensesSentential modifiers can be scope taking (negation, modals,
allegedly, predictably)Tense vs. temporal reference
Nonfinite clauses have no tense but they do have temporal reference
Tense in embedded clauses can be past but temporal reference is to the future
F-Structure to AKR MappingF-Structure to AKR Mapping
Input: F-structures
Output: clausal, abstract KR
Mechanism: packed term rewritingRewriting system controls lookup of external ontologies via Unified Lexicon compositionally-driven transformation to AKR
Transformations:Map words to Wordnet synsetsCanonicalize semantically equivalent but formally distinct
representationsMake conceptual & intensional structure explicitRepresent semantic contribution of particular constructions
F-Structure to AKR MappingF-Structure to AKR Mapping
Input: F-structures
Output: clausal, abstract KR
Mechanism: packed term rewritingRewriting system controls lookup of external ontologies via Unified Lexicon compositionally-driven transformation to AKR
Transformations:Map words to Wordnet synsetsCanonicalize semantically equivalent but formally distinct
representationsMake conceptual & intensional structure explicitRepresent semantic contribution of particular constructions
Basic structure of AKRBasic structure of AKR
Conceptual StructurePredicate-argument structures
Sense disambiguation
Associating roles to arguments and modifiers
Contextual StructureClausal complements
Negation
Sentential modifiers
Temporal StructureRepresentation of temporal expressions
Tense, aspect, temporal modifiers
Ambiguitymanagement
withchoice spaces
girl with a telescope
seeing with a telescope
Conceptual StructureConceptual Structure
Captures basic predicate-argument structures
Maps words to WordNet synsets
Assigns VerbNet roles
subconcept(talk:4,[talk-1,talk-2,speak-3,spill-5,spill_the_beans-1,lecture-1])role(Actor,talk:4,Ed:1)subconcept(Ed:1,[male-2])alias(Ed:1,[Ed])role(cardinality_restriction,Ed:1,sg)
Shared by “Ed talked”, “Ed did not talk” and “Bill will say that Ed talked.”
Temporal StructureTemporal Structure
temporalRel(startsAfterEndingOf,Now,talk:6)
temporalRel(startsAfterEndingOf,say:6,Now)
temporalRel(startsAfterEndingOf,say:6,talk:21)
“Bill will say that Ed talked.”
Shared by “Ed talked.” and “Ed did not talk.”
Matrix vs. embedded tense
Canonicalization in conceptual structureCanonicalization in conceptual structure
subconcept(tour:13,[tour-1])
role(Theme,tour:13,John:1) role(Location,tour:13,Europe:21)
subconcept(Europe:21,[location-1])
alias(Europe:21,[Europe])
role(cardinality_restriction,Europe:21,sg)
subconcept(John:1,[male-2])
alias(John:1,[John])
role(cardinality_restriction,John:1,sg)
subconcept(travel:6,[travel-1,travel-2,travel-3,travel-4,travel-5,travel-6])
role(Theme,travel:6,John:1)
role(Location,travel:6,Europe:22)
subconcept(Europe:22,[location-1])
alias(Europe:22,[Europe])
role(cardinality_restriction,Europe:22,sg)
subconcept(John:1,[male-2])
alias(John:1,[John])
role(cardinality_restriction,John:1,sg)
“John took a tour of Europe.”“John traveled around Europe.”
Contextual StructureContextual Structure
context(t)
context(ctx(talk:29))
context(ctx(want:19))
top_context(t)
context_relation(t,ctx(want:19),crel(Topic,say:6))
context_relation(ctx(want:19),ctx(talk:29),crel(Theme,want:19))
Bill said that Ed wanted to talk.
Use of contexts enables flat representations
Contexts as arguments of embedding predicates Contexts as scope markers
Concepts and ContextsConcepts and Contexts
Concepts live outside of contexts.
Still we want to tie the information about concepts to the contexts they relate to.
Existential commitmentsDid something happen?
e.g. Did Ed talk? Did Ed talk according to Bill?
Does something exist?e.g. There is a cat in the yard. There is no cat in the yard.
InstantiabilityInstantiability
An instantiability assertion of a concept-denoting term in a context implies the existence of an instance of that concept in that context.
An uninstantiability assertion of a concept-denoting term in a context implies there is no instance of that concept in that context.
If the denoted concept is of type event, then existence/nonexistence corresponds to truth or falsity.
NegationNegation
Contextual structurecontext(t)context(ctx(talk:12)) new context triggered by negationcontext_relation(t, ctx(talk:12), not:8)antiveridical(t,ctx(talk:12)) interpretation of negation
Local and lifted instantiability assertions instantiable(talk:12, ctx(talk:12)) uninstantiable (talk:12, t) entailment of negation
“Ed did not talk”
Relations between contextsRelations between contexts
Generalized entailment: veridicalIf c2 is veridical with respect to c1,
the information in c2 is part of the information in c1Lifting rule: instantiable(Sk, c2) => instantiable(Sk, c1)
Inconsistency: antiveridicalIf c2 is antiveridical with respect to c1,
the information in c2 is incompatible with the info in c1Lifting rule: instantiable(Sk, c2) => uninstantiable(Sk, c1)
Consistency: averidicalIf c2 is averidical with respect to c1,
the info in c2 is compatible with the information in c1No lifting rule between contexts
Determinants of context relationsDeterminants of context relations
Relation depends on complex interaction ofConceptsLexical entailment classSyntactic environment
ExampleHe didn’t remember to close the window. He doesn’t remember that he closed the window. He doesn’t remember whether he closed the window.
He closed the window.Contradicted by 1Implied by 2Consistent with 3
Embedded clausesEmbedded clauses
The problem is to infer whether an embedded event is instantiable or uninstantiable on the top level.
It is surprising that there are no WMDs in Iraq.
It has been shown that there are no WMDs in Iraq.
==> There are no WMDs in Iraq.
Embedded examples in real textEmbedded examples in real text
From Google:
Song, Seoul's point man, did not forget to persuade the North Koreans to make a “strategic choice” of returning to the bargaining table...
Song persuaded the North Koreans…
The North Koreans made a “strategic choice”…
Semantic relationsSemantic relations
Presupposition (Factive verbs, Implicative verbs)It is surprising that there are no WMDs in Iraq.
It is not surprising that there are no WMDs in Iraq.Is it surprising that there are no WMDs in Iraq?If it is surprising that there are no WMDs in Iraq, it is because we
had good reasons to think otherwise.
Entailment (Implicative verbs)It has been shown that there are no WMDs in Iraq.
It has not been shown that there are no WMDs in Iraq.Has it been shown that there are no WMDs in Iraq?If it has been shown that there are no WMDs in Iraq, the war has
turned out to be a mistake.
FactivesFactives
Class Inference Pattern
Positive
Negative
+-/+ forget that forget that X ⇝ X, not forget that X ⇝ X
+-/- pretend that pretend that X not ⇝ X, not pretend that X not ⇝ X
ImplicativesImplicatives
++/-- manage to
+-/-+ fail to
manage to X ⇝ X, not manage to X not ⇝ X
fail to X not ⇝ X, not fail to X ⇝ X
++ force to force X to Y ⇝ Y
+- prevent from prevent X from Ying not Y⇝
-- be able to not be able to X not X⇝
-+ hesitate to not hesitate to X X⇝
Class Inference Pattern
Two-wayimplicatives
One-wayimplicatives
Implicatives under FactivesImplicatives under Factives
It is surprising that Bush dared to lie.
It is not surprising that Bush dared to lie.
Bush lied.
Phrasal ImplicativesPhrasal Implicatives
Have
Take
Ability NounChance Noun
Character Noun
= --Implicative= --Implicative= ++/--Implicative
Miss Chance Noun = +-/-+Implicative
Seize Chance Noun = ++/--Implicative
Chance Noun
Effort NounAsset Noun
= ++/--Implicative= ++/--Implicative
= ++/--Implicative
Use Chance NounAsset Noun
= ++/--Implicative= ++/--Implicative
WasteChance Noun
Asset Noun
= +-/-+Implicative
= ++/--Implicative
+
+
+
+
+
+
(ability/means)
(chance/opportunity)(courage/nerve)
(chance/opportunity)(money)(trouble/initiative)
(chance/opportunity)(money)
(chance/opportunity)(money)
(chance/opportunity)
(chance/opportunity)
Conditional verb classesConditional verb classes
Joe had the chutzpah to steal the money. ⇝ Joe stole the money.
Two-way implicativewith “character nouns”
“character noun”(gall, gumption, audacity…)
Relative PolarityRelative Polarity
Veridicality relations between contexts determined on the basis of a recursive calculation of the relative polarity of a given “embedded” context
Globality: The polarity of any context depends on the sequence of potential polarity switches stretching back to the top context
Top-down each complement-taking verb or other clausal modifier, based on its parent context's polarity, either switches, preserves or simply sets the polarity for its embedded context
Example: polarity propagationExample: polarity propagation
“Ed did not forget to force Dave to leave.”
“Dave left.”
Ed
Dave
subj
objsubj comp
comp
comp
subj
not
force
Dave
leave
forget
Ed
+
-
+
+
subj
Dave
leave
Summary of basic structure of AKRSummary of basic structure of AKR
Conceptual StructureTerms representing types of individuals and events, linked to WordNet synonym sets
by subconcept declarations.
Concepts typically have roles associated with them.
Ambiguity is encoded in a space of alternative choices.
Contextual Structuret is the top-level context, some contexts are headed by some event term
Clausal complements, negation and sentential modifiers also introduce contexts.
Contexts can be related in various ways such as veridicality.
Instantiability declarations link concepts to contexts.
Temporal StructureLocating events in time.
Temporal relations between events.
ECDECD
ECD operates on the AKRs of the passage and of the hypothesis
ECD operates on packed AKRs, hence no disambiguation is required for entailment and contradiction detection
If one analysis of the passage entails one analysis of the hypothesis and another analysis of the passage contradicts some other analysis of the hypothesis, the answer returned is AMBIGUOUS
Else: If one analysis of the passage entails one analysis of the hypothesis, the answer returned is YES
If one analysis of the passage contradicts one analysis of the hypothesis, the answer returned is NO
Else: The answer returned is UNKNOWN
AKR (Abstract Knowledge AKR (Abstract Knowledge Representation)Representation)
More specific entails less specificMore specific entails less specific
How ECD worksHow ECD works
Kim hopped.
Someone moved.
Text:
Hypothesis:Alignment
Specificitycomputation
Elimination ofElimination ofH facts that areH facts that are
entailed by T facts.entailed by T facts.
Kim hopped.
Someone moved.
Text:
Hypothesis:
Kim hopped.Text:
Hypothesis:
t
t
t
t
t
t
Context
Someone moved.
Alignment and specificity computationAlignment and specificity computation
Specificitycomputation
Alignment
Every (↓) (↑) Some (↑) (↑)
Every boy saw a small cat.
Every small boy saw a cat.
Text:
Hypothesis:
Every boy saw a small cat.
Every small boy saw a cat.
Text:
Hypothesis:
Every boy saw a small cat.
Every small boy saw a cat.
Text:
Hypothesis:
t
t
t
t
t
t
Context
Elimination of entailed termsElimination of entailed terms
Every boy saw a small cat.
Every small boy saw a cat.
Text:
Hypothesis:
t
t
Every boy saw a small cat.
Every small boy saw a cat.
Text:
Hypothesis:
t
t
Every boy saw a small cat.
Every small boy saw a cat.
Text:
Hypothesis:
t
t
Context
Contradiction:Contradiction:instantiable --- uninstantiableinstantiable --- uninstantiable
Stages of ECDStages of ECD
1. WordNet and Alias alignment for (un)instantiable concepts in conclusion
1a Returns < = > depending on hyperlists of terms 1b Returns < = > depending on theory of names (assuming 1a
matched)2. Make extra top contexts for special cases — e.g. Making head of
question (below) interrogative a top_context3. Context alignment Any top context in conclusion aligns with any top context in
premise Any non-top_context in conclusion aligns with any non top_context
in premise if their context_heads align in stage 14. paired_roles are saved (roles with the same role name in
premise and conclusion on aligned concepts)
Stages of ECDStages of ECD
6. unpaired roles in premise and conclusion (both) makes concepts not align.
7. cardinality restrictions on concepts are checked and modify
alignment direction (including dropping inconsistent alignments)
8. Paired roles are checked to see how their value specificity affects alignment
9. Temporal modifiers are used to modify alignment10. Instantiable concepts in the conclusion are removed if there is
an more specific concept instantiable in an aligned context in premise.
11. Conversely for uninstantiable12. Contradiction checked (instantiable in premise and
uninstantiable in conclusion, and vice versa)
AKR modificationsAKR modifications
AKR0
P-AKR
Q-AKR
simplify
augment
Oswald killed Kennedy => Kennedy died.
Kim managed to hop. => Kim hopped.
normalize
The situation improved.
The situation became better.
=>
From temporal modifiers to temporal From temporal modifiers to temporal relationsrelations
Inventory of temporal relations: the Allen relations plus certain disjunctions thereof
Recognize the type of temporal modifiere.g. bare modifiers, “in” PPs, “for” PPs
Ed visited us Monday/that week/every day.Ed slept the last two hours.Ed will arrive a day from/after tomorrow.
Represent the interval specified in the temporal modifierLocate intervals designated by temporal expressions on time axisDetermine qualitative relations among time intervals
Interpretation of temporal expressionsInterpretation of temporal expressions
Compositional make-up determines qualitative relationsRelative ordering can be all a sentence specifies
Reference of calendrical expressions depends on interpretation of tense
Two different computationsDetermine qualitative relations among time intervals
Locate intervals designated by temporal expressions on time axis
Infer relations not explicitly mentioned in textSome through simple transitive closure
Others require world/domain knowledge
Temporal modification under negation and Temporal modification under negation and quantificationquantification
Temporal modifiers affect monotonicity-based inferences
Everyone arrived in the first week of July 2000.Everyone arrived in July 2000.YESNo one arrived in July 2000.No one arrived in the first week of July 2000.YES
Everyone stayed throughout the concert.Everyone stayed throughout the first part of the concert.YESNo one stayed throughout the concert.No one stayed throughout the first part of the concert.UNKNOWN
Quantified modifiers and monotonicityQuantified modifiers and monotonicity
Many inference patterns do not depend on calendrical anchoring but on basic monotonicity properties
Monotonicity-based inferences depend on implicit dependencies being represented
Last year, in September, he visited us every day.Last year he visited us every day.UNKNOWNLast year he visited us every day.Last year he visited us every day in September.YES
Every boy bought a toy from Ed.Every boy bought a toy.YESEvery boy bought a toy.Every boy bought a toy from Ed.UNKNOWN
Allen Interval RelationsAllen Interval RelationsRelation Illustration Interpretation
X < YY > X
X _ _ Y _
X takes place before Y
X m YY mi X
_ X _ _ Y _
X meets Y (i stands for inverse
X o YY oi X
_ X _ _ Y _
X overlaps Y
X s YY si X
_ X __ Y _
X starts Y
X d YY di X
_ X __ Y _
X during Y
X F YY fi X
_ X _ _ Y _
X finishes Y
X = Y_ X _ _ Y _
X is equal to Y(X is cotemporal with Y)
Qualitative relations of intervals and Qualitative relations of intervals and eventsevents
Left boundary Right boundary
throughout
NOWwithin
Determining the relevant interval
Determining the relation between interval and event
Taking negation and quantification into consideration
From language to qualitative relations From language to qualitative relations of intervals and eventsof intervals and events
Left boundary Right boundary
throughoutNOW
Ed has been living in Athens for 3 years.Mary visited Athens in the last 2 years.
Mary visited Athens while Ed lived in Athens.
Ed’s living in Athens Mary’s visit to Athens
within
Left boundary
From English to AKRFrom English to AKR
Ed has been living in Athens for 3 years.trole(duration,extended_now:13,interval_size(3,year:17)) trole(when,extended_now:13,interval(finalOverlap,Now))trole(when,live:3,interval(includes,extended_now:13)
Mary visited Athens in the last 2 years.trole(duration,extended_now:10,interval_size(2,year:11))trole(when,extended_now:10,interval(finalOverlap,Now))trole(when,visit:2,interval(included_in,extended_now:10))
Mary visited Athens while Ed lived in Athens.trole(ev_when,live:22,interval(includes,visit:6)) trole(ev_when,visit:6,interval(included_in,live:22))
Quantified modifiers and monotonicityQuantified modifiers and monotonicity
Many inference patterns do not depend on calendrical anchoring but on basic monotonicity properties
Monotonicity-based inferences depend on implicit dependencies being represented
Last year, in September, he visited us every day.Last year he visited us every day.UNKNOWNLast year he visited us every day.Last year he visited us every day in September.YES
Every boy bought a toy from Ed.Every boy bought a toy.YESEvery boy bought a toy.Every boy bought a toy from Ed.UNKNOWN
Distributed modifiersDistributed modifiers
Multiple temporal modifiers are dependent on one anotherImplicit dependencies are made explicit in the
representationEd visited us in July, 1991.
trole(when,visit:1,interval(included_in,date:month(7):18))trole(subinterval,date:month(7):18,date:year(1991):18)
In 1991 Ed visited us in July.trole(when,visit:12,interval(included_in,date:month(7):26))trole(subinterval,date:month(7):26,date:year(1991):4)
In 1991 Ed visited us in July every week.trole(when,visit:12,interval(included_in,week:37))trole(subinterval,week:37,date:month(7):26)trole(subinterval,date:month(7):26,date:year(1991):4)
Associating time points with event Associating time points with event descriptionsdescriptions
Trilobites: 540m‐251m years ago
Ammonites: 400m‐65m years ago
1. There were trilobites before there were
ammonites. TRUE
2. There were ammonites before there were
trilobites. FALSE
3. There were trilobites after there were
ammonites. TRUE
4. There were ammonites after there were
trilobites. TRUE
Associating time points with event Associating time points with event descriptionsdescriptions
1. Ed felt better before every injection was administered to him.ordering wrt last injection
2. Ed felt better after every injection was administered to him.ordering wrt last injection
3. Ed felt better before most injections were administered to him. ordering wrt first injection to tip the balance
4. Ed felt better after most injections were administered to him.ordering wrt first injection to tip the balance
How “before” and “after” orderHow “before” and “after” order
In a modifier of the form before S or after S, we need to derive from S a temporal value to pass on to the preposition.
The default operation takes the end of the earliest interval when S is true.
The temporal asymmetry of this operation produces the appearance of after and before being non-inverses.
TimeBank and TimeMLTimeBank and TimeML
A corpus of 183 news articles annotated by hand with temporal information following the TimeML specification
Events, times and temporal links between them are identified and texts are appropriately annotated
TimeML represents temporal information using four primary tag types: TIMEX3 for temporal expressions EVENT for temporal events SIGNAL for temporal signalsLINK for representing relationships
Semantics of TimeML an open issue
TimeML and AKRTimeML and AKR
ŅPrivately, authorities saye74 Rudolph has becomee76 a focus of their investigatione77.Ņ Human-friendly TimeML: creation_time: t92 Tlinks: l45 saye74,ei2046 includes 19980227t92 l46 investigatione77,ei2048 includes becomee76,ei2047 Slinks: l62 saye74,ei2046 evidential becomee76,ei2047 Alinks: none
AKR excerpt: event(say:8) event(become:13) event(investigate:38) trole(when,become:13,interval(before,Now)) trole(ev_when,become:13,interval(included_in,investigate:38)) trole(when,say:8,interval(includes,Now)) trole(when,say:8,interval(includes,Now))
TimeML-AKR matchTimeML-AKR match
<EVENT eid="e76" class="OCCURRENCE">become</EVENT> <MAKEINSTANCE eventID="e76" eiid="ei2047" tense="PRESENT" aspect="PERFECTIVE" polarity="POS" pos="VERB" />
event(become:13) trole(when,become:13,interval(before,Now))
EVENT eid="e77" class="OCCURRENCE">investigation</EVENT> <MAKEINSTANCE eventID="e76" eiid="ei2047" tense="PRESENT" aspect="PERFECTIVE" polarity="POS" pos="VERB" />
event(investigate:38)
<TLINK lid="l46" relType ="INCLUDES " eventInstanceID="ei2048" relatedToEvent Instance="ei2047" />
trole(ev_when,become:13, interval(included_in,investigate:38))
<EVENT eid="e74" class="REPORTING ">say</EVENT> <MAKEINSTANCE eventID="e74" eiid="ei2046" tense="PRESENT" aspect="NONE" polarity="POS" pos="VERB" />
event(say:8) trole(when,say:8,interval(includes,Now))
Credits for the Bridge SystemCredits for the Bridge System
NLTT (Natural Language Theory and Technology) group at PARCDaniel BobrowBob CheslowCleo CondoravdiDick Crouch*Ronald Kaplan*Lauri KarttunenTracy King* * = now at PowersetJohn MaxwellValeria de Paiva† † = now at CuilAnnie Zaenen
InternsRowan NairnMatt PadenKarl PichottaLucas Champollion
Thank youThank you