1.3.4.3 Search Engine Indexing & PageRank algorithm

Question 1

What are the programs that scour the WWW called

Answer 1

Spiders/crawlers

Question 2

What do spiders do?

Answer 2

Spiders index any pages, content, metadata they find and map links between pages by following all:

Internal links

External links

This updates the index. Updating the index must be done continuously as pages get added/removed/updated

Question 3

What does the PageRank algorithm do and aim to achieve?

Answer 3

It is used to help compile and rank webpages and list of results returned by a search engine.

It checks the number and quality of links to a page, determining roughly how important it is. Those of greater importance are more likely to be linked to from other websites.

Question 4

PR(A) = (1 – d) + d (PR(T1)/C(T1) + … + PR(Tn) / C(Tn))

What does PR(A) mean?

Answer 4

Page rank of page A

Question 5

PR(A) = (1 – d) + d (PR(T1)/C(T1) + … + PR(Tn) / C(Tn))

What does C(Tn) mean?

Answer 5

The total count of outbound links from web page n, including to A

Question 6

PR(A) = (1 – d) + d (PR(T1)/C(T1) + … + PR(Tn) / C(Tn))

What does PR(T1)/C(T1) do?

Answer 6

The share of the vote page A gets from pages T1 to Tn

Question 7

PR(A) = (1 – d) + d (PR(T1)/C(T1) + … + PR(Tn) / C(Tn))

d stands for a damping factor. What is meant by a damping factor?

Answer 7

The damping factor prevents PR(Tn)/C(Tn) from having too much influence. It notionally set to 0.85.