Coreference
Resolution
USING HOBBS‟S ALGORITHM
Hemant Kumar (10579)
Babul Bhanu (10545)
Pratheek Adidela (10583)
Shekhar K...
Contents


What is coreference resolution



Anaphoric and Cataphoric references



Direct and indirect anaphora



Ho...
What is Coreference Resolution


In computational linguistics, Coreference resolution is a well-studied
problem in discou...
Anaphoric and Cataphoric
references


Cataphora
In linguistics, cataphora is used to first insert an expression or word
t...
Hobbs‟s algorithm


Hobbs‟s algorithm is mainly focused on “surface parse tree”. By this is
means that the tree that exhi...
Hobbs‟s algorithm for Hindi


Pronouns in Hindi exhibit a great deal of ambiguity.



Pronouns in the first, second and ...
EXAMPLE 1
Non-Reflexive
pronoun

S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Dr...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
uske

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
uske

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
uske

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
uske

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
uske

VP1

VP

...
Previous
sentence

S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_p...
S1

EXAMPLE 2
Reflexive pronoun

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
apne

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
apne

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
apne

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
apne

VP1

VP

...
S1

VP2

NP_erg(SUB)

Nbar

Noun
Mr.Smith

Postp
ne

NP2_acc(DO)

Nbar

Postp
ko

Noun
Driver
Pronoun_poss
apne

VP1

VP

...
Challenges in implementation


Parts of speech tagger



Richness of word database



In Hindi the gender of noun is id...
Applications


English – Hindi machine translation



Machine learning
THANK YOU
Co reference resolution
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Co-reference resolution..Pronominal resolution using Hobb's algorithm

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Co reference resolution

  1. 1. Coreference Resolution USING HOBBS‟S ALGORITHM Hemant Kumar (10579) Babul Bhanu (10545) Pratheek Adidela (10583) Shekhar Kumar (09562)
  2. 2. Contents  What is coreference resolution  Anaphoric and Cataphoric references  Direct and indirect anaphora  Hobbs‟s algorithm  Hobb‟s algorithm for Hindi  Problems in implementation  Applications
  3. 3. What is Coreference Resolution  In computational linguistics, Coreference resolution is a well-studied problem in discourse. To derive the correct interpretation of text, or even to estimate the relative importance of various mentioned subjects, pronouns and other referring expressions must be connected to the right individuals.  There are two types of references: When the reader must look back to the previous context, Coreference is called anaphoric reference. When the reader must look forward, it is cataphoric reference.
  4. 4. Anaphoric and Cataphoric references  Cataphora In linguistics, cataphora is used to first insert an expression or word that co-refers with a later expression in the discourse. An example of strict, sentence-internal cataphora in English is the following sentence “When he arrived home, John went to sleep.”  Anaphora In linguistics, anaphora is the use of an expression the interpretation of which depends upon another expression in context (its antecedent or postcedent).In the sentence “Sally arrived, but nobody saw her” the pronoun „her‟ is anaphoric, referring back to Sally.
  5. 5. Hobbs‟s algorithm  Hobbs‟s algorithm is mainly focused on “surface parse tree”. By this is means that the tree that exhibits the grammatical structure of the sentences (its division into subject, verb, objects, adverbials, etc.) without permuting or omitting any of the words in a sentence.  The naïve algorithm traverses the surface parse tree in a particular order looking for a noun phrase of the correct gender and number.
  6. 6. Hobbs‟s algorithm for Hindi  Pronouns in Hindi exhibit a great deal of ambiguity.  Pronouns in the first, second and third person do not convey any information about the gender  Redefined the grammar for Hindi
  7. 7. EXAMPLE 1 Non-Reflexive pronoun S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  8. 8. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  9. 9. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  10. 10. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  11. 11. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  12. 12. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  13. 13. Previous sentence S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss uske VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  14. 14. S1 EXAMPLE 2 Reflexive pronoun VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss apne VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  15. 15. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss apne VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  16. 16. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss apne VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  17. 17. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss apne VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  18. 18. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss apne VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  19. 19. S1 VP2 NP_erg(SUB) Nbar Noun Mr.Smith Postp ne NP2_acc(DO) Nbar Postp ko Noun Driver Pronoun_poss apne VP1 VP PP_loc NP1(PO) postp mein Nbar Noun truck Verb dekha
  20. 20. Challenges in implementation  Parts of speech tagger  Richness of word database  In Hindi the gender of noun is identified by using verbs
  21. 21. Applications  English – Hindi machine translation  Machine learning
  22. 22. THANK YOU

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