Revise Computingrevisecomputing.co.uk
Free student revisionSee questionsFor schoolsSchool enquiry
Free revisionSee questionsFor schoolsSchool enquiry
Knowledge/A Level/H446/01 Computer systems/Web Technologies/PageRank algorithm

PageRank algorithm

1.3.4 Web Technologies

Practise exam questions

Web Technologies — Note 3 of 4

Candidates should understand how PageRank ranks search engine results. Candidates should understand how page rank works at a high level but are not expected to be able to code the algorithm.

What you need to know

PageRank is an algorithm used to rank web pages in search results. It works on the idea that a page is important if many other important pages link to it. You need to understand how it works at a high level, but you will not be asked to code it.

What to know

  • Each link to a page counts as a 'vote' for it. Links from pages with a high PageRank are worth more than links from pages with a low PageRank.
  • A page's vote is shared between all the links on it, so a link from a page with many outgoing links is worth less.
  • The damping factor d (usually about 0.85) represents the probability that a user keeps clicking links rather than starting a new search.
  • PageRank is calculated iteratively: starting values are assigned, and the calculation is repeated until the values settle.
  • PageRank is only one of many factors used to order results; relevance to the search terms also matters.

Key terms

Exam tipCommon mistake

PageRank

An algorithm that estimates the importance of a web page based on the number and quality of the pages that link to it.

  • Common mistake: Saying PageRank counts how many times a page is visited. It is based on links between pages, not visits.

Exam technique

  • Tip:You may be asked to apply the formula to a small set of pages for one iteration, or to explain why one page ranks higher than another.

Code examples

The PageRank formula
text
PR(A) = (1 - d) + d ( PR(T1)/C(T1) + ... + PR(Tn)/C(Tn) )

PR(A)   PageRank of page A
T1..Tn  pages that link to page A
C(T)    number of outbound links on page T
d       damping factor, usually 0.85

Ready to test yourself?

Practise 1.3.4 questions
← Previous noteSearch engine indexing1.3.4 Web TechnologiesNext note →Server and client side processing1.3.4 Web Technologies

Back to Web Technologies

Web Technologies

Note 3 of 4

  1. 1HTML, CSS and JavaScript
  2. 2Search engine indexing
  3. 3PageRank algorithm
  4. 4Server and client side processing
Topic overview