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

• Previously Discussed Topics
• Session Outcomes
• First Order Logic
• Components of FOL
• Constants
• Variables
• Predicates
• Functions
• Logical Connectives

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Previously Discussed Topics

LBRCE

NLP

• Examples of Logical connectives
• Quantifiers
• Examples of Quantifiers
• Exercises and Solutions
• Representing events
• Inference Using FOL
• Advantages of FOL
• Disadvantages of FOL

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Previously Discussed Topics

LBRCE

NLP

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

• Apply Description logics to derive meaning of the sentences (Apply-L3)

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Session Outcomes

LBRCE

NLP

• Description Logics (DL) are a family of formal knowledge representation languages used to represent concepts (classes), relationships, and individuals in a domain.
• DL is mainly used in:
• Knowledge representation
• Ontology modeling
• Semantic Web
• Natural Language Processing
• It allows computers to describe structured knowledge and reason about it automatically.

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Description Logic

LBRCE

NLP

• Concepts
• Roles
• Individuals

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Components of DL

LBRCE

NLP

• A concept represents a set or category of objects in a domain.
• Concepts are similar to classes in object-oriented programming.
• Examples: Person, Student, Teacher, Animal, Vehicle
• Example statement: Student ⊆ Person
• Meaning: All students are persons.
• Example Representation
• Sentence: Ravi is a student.
• Representation:Student(Ravi)
• Explanation: Ravi belongs to the concept Student.

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Concepts (Classes)

LBRCE

NLP

• A role represents a relationship between two concepts or individuals.
• Roles are similar to relations in databases.
• Examples: hasChild, teaches, owns, livesIn, drives
• Example
• Sentence: John teaches Ravi.
• Representation: teaches(John, Ravi)

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Roles (Relationships)

LBRCE

NLP

• Here
• John → teacher
• Ravi → student
• teaches → role
• Example with Concepts
• Teacher ⊆ Person�Student ⊆ Person
• Relationship: teaches(Teacher, Student)
• Meaning: Teachers teach students.

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Roles (Relationships)

LBRCE

NLP

• Individuals represent specific objects or entities in the domain.
• Examples: John, Ravi, Sita, Paris, Car1
• Example
• Student(Ravi)�Teacher(John)
• Meaning
• Ravi is a student
• John is a teacher

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Individuals (Instances)

LBRCE

NLP

• A DL knowledge base consists of two parts:
• TBox (Terminological Box)
• ABox (Assertional Box)

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

DL Knowledge Base

LBRCE

NLP

• TBox contains general knowledge about concepts and relationships.
• Example
• Student ⊆ Person�Teacher ⊆ Person�Doctor ⊆ Person
• Meaning
• Students are persons
• Teachers are persons
• Example: Parent ≡ Person ⊓ ∃hasChild.Person
• Meaning: A parent is a person who has at least one child.

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Terminological Box (Tbox)

LBRCE

NLP

• ABox contains specific facts about individuals.
• Example
• Student(Ravi)�Teacher(John)�hasChild(John, Ravi)
• Meaning
• Ravi is a student
• John is a teacher
• John has a child Ravi

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Assertional Knowledge Box (Abox)

LBRCE

NLP

• DL provides operators to create complex concepts.
• Conjunction (AND)
• Disjunction (OR)
• Negation (NOT)
• Existential Restriction
• Universal Restriction

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Concept Constructors in DL

LBRCE

NLP

• Symbol: ⊓
• Example: Student ⊓ Athlete
• Meaning: Students who are athletes.
• Example sentence
• Ravi is a student and athlete.
• Representation
• (Student ⊓ Athlete)(Ravi)

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Conjunction (AND)

LBRCE

NLP

• Symbol: ⊔
• Example: Student ⊔ Teacher
• Meaning: A person who is either student or teacher.

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Disjunction (OR)

LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Negation (NOT)

• Symbol: ¬
• Example: ¬Student
• Meaning: Not a student.
• Example: ¬Student(John)
• Meaning: John is not a student.

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Existential Restriction

• Symbol:∃
• Example: ∃hasChild.Person
• Meaning: A person who has at least one child.

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Universal Restriction

• Symbol: ∀
• Example: ∀teaches.Student
• Meaning: A person who teaches only students.

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Exercises

• Exercise 1
• Convert the following into description logic representation.
• Sentence
• Ravi is a student.
• Exercise 2
• Represent the following concept.
• Sentence
• A parent is a person who has a child.
• Exercise 3
• Given
• Teacher ⊆ Person�Teacher(John)
• What can be inferred?�

LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Exercises

• Exercise 4
• Represent the sentence using DL.
• Sentence
• All doctors are persons.
• Exercise 5
• Translate the following statement.
• Sentence
• Sita teaches Ravi.

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Solutions

• Exercise 1
• Sentence:Ravi is a student.
• Solution: Student(Ravi)
• Exercise 2
• Sentence: A parent is a person who has a child.
• Solution: Parent ≡ Person ⊓ ∃hasChild.Person
• Exercise 3
• Given
• Teacher ⊆ Person�Teacher(John)
• What can be inferred?
• Solution: Person(John)
• Explanation”Since teachers are persons, John must be a person.

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Solutions

• Exercise 4
• Sentence: All doctors are persons.
• Solution: Doctor ⊆ Person
• Exercise 5
• Sentence: Sita teaches Ravi.
• Solution: teaches(Sita, Ravi)

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Advantages of DL

• Structured knowledge representation
• Supports reasoning and inference
• Used in ontologies like OWL
• Helps build semantic knowledge bases
• Useful for NLP semantic understanding

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LBRCE

NLP

S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Disadvantages of DL

• Cannot easily represent uncertainty
• Complex reasoning for large knowledge bases
• Limited ability for procedural knowledge

LBRCE

NLP

• Previously Discussed Topics
• Session Outcomes
• Description Logic
• Components of DL
• Concepts (Classes)
• Roles (Relationships)
• Individuals (Instances)
• DL Knowledge Base
• Terminological Box (TBOX)

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Summary

LBRCE

NLP

• Assertional Knowledge (ABox)
• Concept Constructors in DL
• Conjunction (AND)
• Disjunction (OR)
• Negation (NOT)
• Existential Restriction
• Universal Restriction
• Exercises
• Solutions
• Advantages of DL
• Disadvantages of DL

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S.V.V.D.Jagadeesh

Saturday, March 7, 2026

Summary

LBRCE

NLP