Synonymy and Near-Synonymy in Deep Lexical Semantics

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Synonymy and Near-Synonymyin Deep Lexical
Semantics

• Niloofar Montazeri and Jerry R. Hobbs
• Information Sciences Institute
• University of Southern California
• Marina del Rey, CA

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Deep Lexical SemanticsMethodology
words
link with axioms
core theories
Construct core theories of abstract phenomena in
various domains Express meanings of word
senses as logical axioms in terms of
predicates in core theories
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Core Theories and Lexical Periphery
Define (Characterize) words in terms supplied by
the core theories. range(x,y,z) lt--gt
scale(s) subscale(s1,s) bottom(y,s1)
top(z,s1) in(u1,x) at(u1,y)
in(u2,x) at(u2,z) (??u ? x)(? v ?
s1) at(u,v)
s
s1
y
z
v
word range
linking axiom
x u1 . . . . . . . u . . . . . u2
core theory
Axiomatize core theories with richly explicated
core predicates Core Theory of Scales scale,
lt, subscale, top, bottom, at
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Abstract Words in Context
By specializing at and the scale in various
ways, we can get a whole range of possible
meanings for range The scores on
the test ranged from 33 to 96. The timber
wolf ranges from Mexico to the Arctic. His
behavior ranged from cheerful to sullen.
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Deep Lexical Semanticsof Event-Related Words
(forall (x y z) (iff (give x y z)
(exist (e1 e2 e3) (and (cause
x e1)(change e1 e2 e3)(have e2 x y)
(have e3 z y))))) x gives y to
z x causes a change from x having y to z having
y Builds on old work by Gruber, Lakoff, Schank,
Jackendoff, and many others on lexical
decomposition, but .... primative predicates
are explicated in core theories restricts
possible interpretations of the predicates
enables reasoning within theory logic, not
syntax
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Use in Textual Inference
T Russia is blocking oil from entering
Ukraine. H Oil cannot be delivered to Ukraine.
Lexical decomposition axioms
not(n2,c2) can(c2,x2,d2) deliver(d2,x2,o2,u
2)
cause(d2,x2,c3) changeTo(c3,h2)
have(h2,u2,o2)
possible(p1,c4) cause(c4,x3,e1)
in(h2,o2,u2)
cause(c1,x1,n1) not(n1,p1) possible(p1,e1)
Defeasible inferences from core theories
block(b1,x1,e1) enter(e1,o1,u1)
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Core Theories Change
change(e1,e2) state e1 changes into state
e2 e1 and e2 involve a common entity
change of state of something Transitive if the
something is the same e1 and e2 are different
unless there is an intermediate state
(cyclic change) move is change of state of
at relation change(e1,e2) changeFrom(e1)
changeTo(e2)
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Theory of Causality Causal Complex
causal complex
s
causal-complex(s,e) e1 ? s, ....
e1
e2
e3
e
e4
....
effect
When every event or state in s happens or holds,
then e happens or holds. All eventualities
in s are relevant to the effect. A rigorous,
nondefeasible notion, but cant specify
everything.
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Theory of Causality Cause
In a causal complex, some eventualities are
distinguished as causes.
Causes are the focus of planning,
prediction, explanation, interpreting discourse (b
ut not diagnosis)
presumable
power on
finger in socket
shock
cause
What is presumable depends on task,
context, knowledge base, .... Cause is a useful
but defeasible notion.
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Methodology
Having axiomatized these core theories,
.... Focus on most common 450 word senses
involving change of state and
causality Determine radial structure of set of
WordNet senses of word, and characterize by
incremental differences in associated
axioms Encode axioms for the most abstract or
general senses or supersenses Evaluate
on a textual entailment task
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Enter
At each hop, we specialize a predicate
or constrain an argument
enter-S1 x enters p changeTo(p(x))
enter-V2 enter a race enter-V4 enter into
calculations enter-V9 enter into career
p at/in
enter-S11 x enters y changeTo(in(x,y))
enter-V1 enter a room enter-V6 enter from
stage left
cause
enter-S2 x enters y in z cause(x,enter-S11(y
,z)) enter-V5 enter in ledger enter-V8
enter picture into text
Logically, and sometimes chronologically
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Hit
Supersenses give topological
structure. Specific senses specialize
general predicates or put constraints on
arguments
hit-S1 x hits y changeTo(at(x,y)) We hit
Detroit by noon. The temperature hit -20.
sudden impact
hit-S11 x hits y changeTo(e,in(x,y))
sudden(e) impact(x,y) The car hit a
tree.
cause
hit-S2 x hits z with y cause(x,hit-S11(y,z))
He hit the ball.
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Synonymy and Near-Synonymy
Synonymy The axiomatic lexical decompositions
are the same Near-synonymy The axiomatic
lexical decompositions differ only
incrementally (similar to word senses in
radial structure)
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Receive and Get
receive-S1 x receives y from z
change(have(z,y), have(x,y)) -gt
changeTo(have(x,y)) FrameNet sense 1
subsumes all of WordNets senses where
have is specialized to owning, having a
property, perceiving, hosting,
etc. get-S11 x gets y cause(x,
changeTo(have(x,y))) He always gets what he
wants. Ill get the book at the
library. get-S12 x gets y
changeTo(have(x,y)) He got the flu. I
got a call from Sue. Youll get your results
tomorrow.
Synonyms or near-synonyms
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Go, Hit, and Reach
x is an argument of ei or a participant in ei
go-V1 x goes from e1 to e2 change(e1,e2)
arg(x,e1) arg(x,e2) go-FV3 specialize
e1 and e2 to at relations x goes from y to
z change(at(x,y), at(x,z)) hit-S1 x
hits z changeTo(at(x,z)) reach-S1 x
reaches z changeTo(at(x,z))
3rd FrameNet sense
Not synonymous at more general levels of go
Not synonymous at more specific levels of hit
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Deliver, Give, and Provide
deliver-S1 x delivers y from w to z
cause(x, change(rel(y,w), rel(y,z))) deliver-S11
specializes rel to have stipulate that x w
cause(x, change(have(x,y), have(z,y))) give-S0
cause(x, exist(y)) give-S1 cause(x,
change(have(x,y), have(z,y))) provide-S1 x
provides z with y cause(x,
changeTo(possible(e))) arg(y,e) need(z,e)
provide for medical emergencies provide-S11
possible(e) specializes to have(z,y)
cause(x, changeTo(have(z,y))) need(z,e)
synonyms
near synonyms
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An Aside on Need
(Gordon Hobbs)
In a core theory of cognition (based on beliefs
and goals), Define badFor(e,x) e causes a goal
of xs not to happen need(x,e) cause(not(e),
e1) badFor(e1,x)
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Overlapping Radial Structures
deliver-S1
give-S0
provide-S1
give-S1
deliver-S11
provide-S11
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A Problem
Synonymy is a relation between word
senses. Carving the uses of words into word
senses is highly arbitrary e.g., WordNet is
very fine-grained VerbNet less so.
word-1, sense-i
word-2, sense-j
Why not just stipulate that these are three
different senses, so that in the middle the
senses are perfectly synonymous?
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Context-Dependent Synonymy
give cause to have provide cause to have
need She gave food to the hungry man. She
provided food for the hungry man. The sentences
are equivalent even though give and provide
are only near synonyms.
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Synonymous Specific Senses
So far the examples have been at an abstract
level, but intersection of radial structures
can occur at very specific levels
too deliver-V1 deliver a talk give-V12
give a talk
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Small Perspective DifferencesNear Synonyms?
hold x holds e cause(x,
not(changeFrom(e))) hold that
pose Specialize e to at cause(x,
not(changeFrom(at(y,z)))) hold the picture
against the wall block x blocks e
cause(x, not(changeTo(e))) The senator
blocked the judges appointment Specialize e to
at cause(x, not(changeTo(at(y,z)))) He
blocked my way These can describe the same
situation hold(x,e) block(x,not(e))
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Capture and Seize
x holds y cause(x, not(changeFrom(at(y,z))))
x captures y cause(x, changeTo(hold(x,y))) Se
ize Almost all senses of seize subsumed
under seize-S1 x seizes y cause(e, x,
changeTo(hold(x,y))) forceful(e)
near synonyms
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Text Entailment ExampleSynonymy from Inference
H The captors let the hostage go free.
let(x,e7) go(e17,y,e8) free(e8,y,c,e9)
not(e5) cause(e5,x,e6) not(e6,e7)
changeTo(e7,e8)
not(e8,e10) cause(e10,c,e11) not(e11,e9)
move(e9,y,z,w)
changeFrom(e9,e12) at(e12,y,z)
Rexist(e0)
changeFrom(e0,e1) cause(e1,x,e2)
not(e2,e3) changeFrom(e3,e4) at(e4,y,z)
release(x,y,z)
T A Filipino hostage in Iraq was released.
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Blunder and Lapse
(Edmunds Hirst)
blunder(e,x) error(e,x) cause(e1,e)
stupid(e1,x) lapse(e,x) error(e,x)
cause(e1,e) neglectful(e1,x)
Need to capture meaning of error in theory of
composite entities as a mismatch between a
composite entity and a pattern that serves
as a norm. Need to capture meanings of stupid
and neglect in theory of cognition
stupid in terms of ability to learn and reason
neglect in terms of model of attention
(Gordon Hobbs)
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Near Synonyms?
raise(x,y,z,w) cause(x, change(at(y,z),
at(y,w))) above(w,z) rise(y,z,w)
change(at(y,z), at(y,w)) above(w,z) Differ
only by cause(x, ...) raise(x,y,z,w) cause(x,
change(at(y,z), at(y,w))) above(w,z) lower(x,y,
z,w) cause(x, change(at(y,z), at(y,w)))
above(z,w) Differ only in relation of w and
z To be near synonyms the words have to
describe the same situations.
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Message
The meanings of word senses can be expressed as
axioms in terms of predicates from core
theories of the relevant phenomena. The
word senses of any word form a radial structure,
where adjacent nodes differ by incremental
changes in the axioms (specializations of
predicates, constraints on arguments). Word
senses of different words can have identical
axiomatic decompositions this is
synonymy. Word senses of different words can
have nearly identical axiomatic
decompositions -- is this near synonymy? Is near
synonymy a natural kind, about which we can make
reliable judgments? More important than
labeling word senses as near synonyms is
capturing the distinctions formally.