CS621 : Artificial Intelligence

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

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

3. Fundamental Triple • <Object, Attribute, Value> • E.g., • <Person, Name, ‘Ram’> • <City, Population, 500000> • <Box, Number, 23> • And so on

4. Review of Predicate Calculus

5. 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

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

7. 10 7 12 5 4 13 14 2 11 15 16 13 2 17

8. Ontology

9. Taxonomic organization of knowledge

10. Simple Inference

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

12. Markup (embeds meta-information) • I just got a new dog • <sentence> <person href="http://aaronsw.com/">I</person> just got a new pet <animal>dog</animal>.</sentence> • <sentence> <person href="http://aaronsw.com">I</person> just got a new pet <animal type="dog" href="http://aaronsw.com/myDog">dog</animal>.</sentence>

13. Namespace • Give meaning to a name • Specifically, bind a name with an URI (uniform resource identifier in the web) • <aref http://www.cse.iitb.ac.in/~pb> Pushpak </aref> {person} • <aref http://www.imdb.com/title/tt0251355/> Pushpak </aref> {movie}

14. Draw the names from the namespace <sentence    xmlns="http://example.org/xml/documents/"    xmlns:c="http://animals.example.net/xmlns/"<c:person c:href="http://aaronsw.com/">I</c:person> just got a new pet <c:animal>dog</c:animal>.</sentence>

15. 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

16. Example (from W3C specification of RDF) • In natural Language • http://www.example.org/index.html has a creator whose value is John Smith • http://www.example.org/index.html has a creation-date whose value is August 16, 1999 • http://www.example.org/index.html has a language whose value is English

17. Subject-Predicate-Object based scheme • the subject is the URL http://www.example.org/index.html • the predicate is the word "creator" • the object is the phrase "John Smith"

18. More concretely through URIs • a subject http://www.example.org/index.html • a predicate http://purl.org/dc/elements/1.1/creator • and an object http://www.example.org/staffid/85740

19. In graphical form

20. With all other information

21. In triple notation • Subject • http://www.example.org/index.html • http://purl.org/dc/elements/1.1/creator> • http://www.example.org/staffid/85740 • Predicate • http://www.example.org/index.html • <http://www.example.org/terms/creation-date> • "August 16, 1999" . • Object • http://www.example.org/index.html • http://purl.org/dc/elements/1.1/language • "en" .