Wsd as distributed constraint optimization problem

WSD as Distributed Constraint
Optimization Problem

Author: Siva Reddy, Abhilash Inumella
Publication: ACL 2010
Presenter: Po-Han Lin (林伯翰)

Outline

 Background
 WSD as a DCOP
 Experiment
 Conclusion and Future
 References

Outline

 Background
 WSD
 COP
 DCOP
 WSD as a DCOP
 Experiment
 Conclusion and Future
 References

Word Sense Disambiguation

 Word Sense Disambiguation (WSD)
 The problem of WSD can be defined as the task
of assigning the most appropriate sense to the
word within a given context.
 WSD is one of the oldest problems in
computational linguistics which dates back to
early 1950’s.
 Example:
 Noun orange has at least two senses:
 color or fruit.

Constraint Optimization Problem

 A COP can be defined as a regular constraint
satisfaction problem in which constraints are
weighted and the goal is to find a solution
maximizing the weight of satisfied constraints.

x is a vector residing in a n-dimensional space
f(x) is a scalar valued objective function,
gi(x) = ci for i = 1, …, n and
hj(x) ≦ dj for j = 1, …, m are constraint functions that need to be satisfied.

Distributed Constraint Optimization
Problem
 DCOP is the distributed analogue to
constraint optimization.
 DCOP is a problem in which a group of
agents must distributedly choose values for a
set of variables such that the cost of a set of
constraints over the variables is either
minimized or maximized.
 DCOP can be formalized as a tuple
 (A, V, D, C, F)

Distributed Constraint Optimization
Problem - (A, V, D, C, F)


Detial about Constraints
 Part-of-speech (POS 詞性)
 Different POS can decide different domain of words.
 Ex: play has 47 senses, but only 17 senses correspond to noun category.
 Morphology (構詞學)
 Word form (字形)
 Vocabulary (字詞)
 orange has color and fruit two senses, but oranges only be used in the fruit sense.
 Domain information
 Information can be captured using a unary utility function defined for every word.
 Sense Relatedness
 Sense relatedness between senses of two words wi, wj is captured by a function f, where f
returns sense relatedness (utility) between senses based on sense taxonomy and gloss
overlaps.
 Discourse
 Many different word, but same sense.
 Collocations
 co-occur word.
 Ex: bank:
 financial institution
 the edge of a river
 if in a given context bank co-occur with money, “financial institution”

Experiment

 Experiment Data
 SENSEVAL-2
 SENSEVAL-3
 Ex:
 <instance id="activate.v.bnc.00024693" docsrc="BNC">
 <answer instance="activate.v.bnc.00024693"
senseid="38201"/>
 <context>
… which you step on to <head>activate</head> it . Used
correctly , … .
 </context>
 </instance>

 Answer
 <lexelt item="activate.v">
 <sense id="38201" source="ws"
wn="activate%2:36:00::" synset="activate actuate
energize start stimulate" gloss="to initiate action in;
make active."/>
 <sense id="38202" source="ws"
wn="activate%2:30:03::" synset="activate" gloss="in
chemistry, to make more reactive, as by heating."/>
 …
 </lexelt>

Experiment
 Experiment Results
 Dcop:
 This paper method
 Sinha07
 Sinha and Mihalcea, 2007
 page rank algorithm
 Agirre09
 Agirre and Soroa, 2009
 page rank algorithm
 used additional knowledge
 extended WordNet relations
 sense disambiguated gloss.
 MFS
 most frequent sense
 popular back-off heuristic in
WSD system.

Conclusion

 Modelling WSD in a distributed constraint
optimization framework.
 Showed that this framework is powerful
enough to encode information from various
knowledge sources.

FutureWork

 Only used relatedness based utility functions
derived from WordNet.
 Effect of other knowledge sources remains to
be evaluated individually and in combination.
 The best possible combination of weights (zk)
of knowledge sources is yet to be
engineered.

References
 WSD as a Distributed Constraint Optimization Problem
 http://dl.acm.org/citation.cfm?id=1858916
 Distributed Constraint Optimization Problem
 http://www.doc88.com/p-23745051258.html
 http://en.wikipedia.org/wiki/Distributed_constraint_optimization
 Constraint optimization
 http://en.wikipedia.org/wiki/Constraint_optimization
 Word Sense Disambiguation
 http://wordnet.princeton.edu/
 http://203.64.42.21/course/2005/tgbcl/poko/ohcl-13.htm
 http://www.scholarpedia.org/article/Word_sense_disambiguation
 SENSEVAL
 http://www.senseval.org/

Wsd as distributed constraint optimization problem

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