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. Issues
Cycles:

8. Issues
Cycles:

9. Issues
Cycles: …

10. 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

11. Results
Results of many random sessions:

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

13. Cycle Buster
Random surfer not phased by cycles:

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

15. Simulator PageRank Simulator:

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

17. Excel Simulation
Three pages:

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

19. Issues Spam Links Discourage with negative weight Spam Link Pages -1

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. "If you're not paying for the product, you are the product."
Power
Controlling search is power:
"If you're not paying for the product, you are the product."