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Natural Language Processing

By

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S.V.V.D.Jagadeesh

Sr. Assistant Professor

Dept of Artificial Intelligence & Data Science

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LAKIREDDY BALI REDDY COLLEGE OF ENGINEERING

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At the end of this session, Student will be able to:

  • Understand coreference(understand-l2)

S.V.V.D.Jagadeesh

Monday, April 6, 2026

Session Outcomes

LBRCE

NLP

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Coreference

LBRCE

NLP

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  • Pronominal Coreference: When a pronoun refers to a previously mentioned noun (antecedent).
  • John went to the bank. He deposited money.
  • Coreference: He → John
  • Nominal Coreference: When two noun phrases refer to the same entity.
  • The boy entered the room. The child sat down.
  • Coreference: boy → child

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Types of Coreference

LBRCE

NLP

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  • Proper Noun Coreference: When different mentions of a proper noun refer to the same entity.
  • Barack Obama gave a speech. Obama inspired many.
  • Coreference: Barack Obama → Obama
  • Split (plural) Coreference: When multiple entities combine and are referred to collectively.
  • John met Mary. They went shopping.
  • Coreference: They → John + Mary

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Types of Coreference

LBRCE

NLP

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  • Appositive Coreference: When two noun phrases are placed side-by-side and refer to the same entity.
  • Rahul, the manager, approved the request.
  • Coreference: Rahul = the manager
  • Predicate Nominal Coreference: Occurs when subject and complement refer to the same entity.
  • John is a teacher.
  • Coreference: John = teacher

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Types of Coreference

LBRCE

NLP

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  • Cataphoric Coreference: When a pronoun refers to an entity mentioned later in the sentence.
  • When he arrived, John sat down.
  • Coreference: he → John
  • Bridging (Associative) Coreference: When two expressions are related indirectly but not identical.
  • I bought a car. The engine is powerful.
  • Relation: engine → part of car

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Types of Coreference

LBRCE

NLP

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  • Exophoric Coreference: Reference to something outside the discourse.
  • Look at that!
  • Coreference: “that” → external object

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Types of Coreference

LBRCE

NLP

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  • Coreference resolution is the task of identifying all expressions that refer to the same entity and grouping them into coreference chains.
  • Chains={C1​,C2​,...,Cn​}

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Coreference Resolution

LBRCE

NLP

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  • Example: John went to the bank. He deposited money. The man left.
  • Step1: Identify mentions- Locate all noun phrases or pronouns that could refer to an entity.
  • {John,He,money,The man}
  • Step2: Extract Features- Analyze features like gender, number, semantic and syntactic positions
  • John(Male, Singular) matches with he (Male, Singular)
  • Step3: Generate Candidate Pairs- Group potential references into chains based on matching features
  • (He,John),(The man,John)

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Steps for Coreference Resolution

LBRCE

NLP

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  • Step4: Resolve Corefernce-Use either rule based or ML based or Neural Network models to resolve coreference

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S.V.V.D.Jagadeesh

Monday, April 6, 2026

Steps for Coreference Resolution

Pair

Gender

Number

Distance

He–John

match

match

small

The man–John

match

match

medium

 

LBRCE

NLP