First order logic

First order logic in AI

1. ARTIFICIAL INTELLIGENCE OMega TechEd 20 First Order Logic

2. OMega TechEd Subscribe First Order Logic First-order logic is another way of knowledge representation in artificial intelligence. It is an extension to propositional  logic. First - order logic  is also known as Predicate   logic  or  First-order predicate logic. Propositional logic assumes the world contain facts . First order logic assumes the world contains Object, relations and function relation . Objects: Person, numbers… Relations: brother of, part of,… Function Relation: father of, best friend,…

3. Predicate Logic Example A sentence in  first - order logic  is written in the form Px or P(x), where P  is the predicate  and x  is the  subject(object), represented as a variable. John is tall. t all(John) John is Subject and tall is predicate Arun and Vijay are friends. friends(Arun , Vijay). OMega TechEd Subscribe

4. Basic Elements of First Order Logic Elements Examples Constant 1, 2, Pune, Ajay… Variables x, y, a , b,… Predicates Brother, Father,… Function Sqrt, LeftLegOf ,… Connectives ^, V, ¬, Equality == Quantifier Ɐ, Ǝ Subscribe OMega TechEd

5. Quantifiers In First Order Logic , a sentence can be structured using the Universal quantifier or the Existential quantifier. OMega TechEd Subscribe

6. Some Examples of FOL 1. All kings are person. Ɐx: King(x) person(x) 2. No-one likes noodles. Ɐx: person(x) ¬ likes(x, noodles) 3. Some dog is a pet. Ǝx : (dog(x) ^ pet(x)) 4. Every student pass or fail. Ɐx: (student(x) (pass(x) V fail (x))) 5. If x is a parent of y then x is older than y. OMega TechEd Subscribe Parent( x,y ) older( x,y ) Ɐx Ɐy

7. Properties of Quantifiers Ɐx Ɐy is the same as Ɐy Ɐx Ǝx Ǝy is the same as Ǝy Ǝx Ǝx Ɐy is not the same as Ɐy Ǝx Ǝx Ɐy loves( x,y )- “There is a person who loves everyone in the world” Ɐy Ǝx loves( x,y )-”Everyone in the world is loved by at least one person” Quantifier duality: Each can be expressed using the other. Ɐx likes(x, IceCream ) ¬ Ǝx ¬likes( x,Icecream ) Ǝx plays(x, Cricket) ¬ Ɐx ¬plays(x, Cricket) OMega TechEd Subscribe

8. Self Test Every cat drinks milk. Virat loves Anushka Someone is Laughing Nobody loves George All men are mortal OMega TechEd Subscribe Check your answers in comment box.

9. Thanks For Watching Reference: Artificial Intelligence A Modern Approach Third Edition Peter Norvig and Stuart J. Russell Subscribe Like Share OMega TechEd Next Topic: Forward and Backward Chaining

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