CS621 : Artificial Intelligence Pushpak Bhattacharyya CSE Dept., IIT Bombay Lecture 9 Continuation of Logic and Semantic Web

AI’s view of knowledge Data Information Knowledge Wisdom Increasing Complexity, Sophistication and Refinement. Every level Contains information On HOW the lower Level is USED

Fundamental Triple E.g., And so on

Review of Predicate Calculus

Predicate Calculus Introduction through an example (Zohar Manna, 1974): Problem: A, B and C belong to the Himalayan club. Every member in the club is either a mountain climber or a skier or both. A likes whatever B dislikes and dislikes whatever B likes. A likes rain and snow. No mountain climber likes rain. Every skier likes snow. Is there a member who is a mountain climber and not a skier? Given knowledge has: Facts Rules

Predicate Calculus: Example contd. Let mc denote mountain climber and sk denotes skier. Knowledge representation in the given problem is as follows: 1. member(A) 2. member(B) 3. member(C) 4. ∀ x[member(x) → (mc(x) ∨ sk(x))] 5. ∀ x[mc(x) → ~like(x,rain)] 6. ∀ x[sk(x) → like(x, snow)] 7. ∀ x[like(B, x) → ~like(A, x)] 8. ∀ x[~like(B, x) → like(A, x)] 9. like(A, rain) 10. like(A, snow) 11. Question: ∃ x[member(x) ∧ mc(x) ∧ ~sk(x)] We have to infer the 11 th expression from the given 10. Done through Resolution Refutation.

Ontology

Taxonomic organization of knowledge

Simple Inference

Fundamental relationships Hypernymy Subclass (man mammal Membership (Ram ε man) Meronymy (part whole) (hand part-of body)

Markup (embeds meta- information) I just got a new dog I just got a new pet dog.

Namespace Give meaning to a name Specifically, bind a name with an URI (uniform resource identifier in the web) Pushpak {person} Pushpak {movie}

Draw the names from the namespace I just got a new pet dog.

RDF: Resource Description Format Each RDF statement has three parts: a subject, a predicate and an object Makes statements about resources on the web, uniquely identified by URIs

Example (from W3C specification of RDF) In natural Language has a creator whose value is John Smith has a creation-date whose value is August 16, has a language whose value is English

Subject-Predicate-Object based scheme the subject is the URL the predicate is the word "creator" the object is the phrase "John Smith"

More concretely through URIs a subject a predicate and an object

In graphical form

With all other information

In triple notation Subject Predicate "August 16, 1999". Object "en".