1. 9 Algorithms: PageRank

2. Ranking After matching, have to rank:

3. Index Based Ranking Strategies we could (do) use: – Frequency – Position – Metadata

4. Missing Ingredient Index lacks intra-page information

5. Link Quality Not all links are equal Who do you trust? – CS Prof – World Famous Chef

6. Identifying Authority Links into a page give it authority Page value = sum of authorities of pages linking to it

7. Link Quality More links is easy to abuse Spam Link Pages

8. Issues Spam Links – Discourage with negative weight Spam Link Pages

9. Issues Cycles:

10. Issues Cycles:

11. Issues Cycles: …

12. Random Surfer Simulating a web surfing session – Start at random page – At each page have a chance to Pick a random link to go to Jump to a completely random page

13. Results Results of many random sessions:

14. Results Expressed as percentages, results stabilize – Law of large numbers

15. Cycle Buster Random surfer not phased by cycles:

16. Random Surfer In Use The recipe pages visited by random surfers:

17. Simulator PageRank Simulator: http://caccio.blogdns.net/software/pagerank-simulator

18. The Real Math Markov Chains – Set of states – Each state has probability of leading to other states – Represent as matrix

19. Excel Simulation Three pages:

20. Limitations Still have issues/room for growth – Link Spam – Context of link Where link is on page "Bob's recipe is terrible" vs "Bob's recipe is great" – Lack of semantic knowledge Page's Authority should not be the same for all domains

21. Power Controlling search is power: http://www.bitsbook.com/ "If you're not paying for the product, you are the product."