PageRank algorithm A -level Computer science (OCR) 1.3.4 (c)

What is the PageRank algorithm?

An iterative algorithm used calculate a relative score of each web page using the quality and quantity of the page links.

Each link from one to another increases the page rank score by a factor related to the score of the linked page.

The damping factor is used so that pages don’t have too much influence.

Even is a page has no backlinks it still gets a small score

The page rank is calculated after each crawl.

It then list the results in a search engine. If a website has a higher score, it will appear higher in a list of search results.

What affects the PageRank of a page?

• The number of inbound links to their site.

• The PageRank of the linking sites.

• The number of outward links from their site.

• How secure a page is, is it malware free?

How are pages and links to pages usually represented?

• Usually represented as a weighted, directed graph.

• Pages are nodes.

• Hyperlinks are edges in one direction.

• Weightings are calculated by PageRank.

A company wants to improve the PageRank score of pages on its website. How can it do this?

• Effective use of meta tags that effectively describe the contents of the website.

• Effective use of H1 tags using suitable headings that describe the contents of the website.

• Increase the number of inbound links, ideally ones with a higher PageRank score.

• Increase number of outgoing links.

• Store key words in meta tags, title tags or header tags (H1, H2 etc).

What is the damping factor.

• It represents the probability that a user will continue browsing by following an internal link rather than randomly typing another URL or moving to a new page in the search engine results.

• A value between 0 and 1 (usually 0.85).

• 85% chance that the user will keep following internal links.

How can the damping factor be exploited to increase a PageRank score.

• A well connected internal link structure: since the damping factor assumes a user is more likely to follow internal links, the company should create a strong internal linking structure.

• Quality outbound links: These links reduce the effectiveness of the damping factor as they bring more users who are more likely to follow internal links.

• Create a balanced link distribution: by spreading out internal links more evenly, the website can ensure that each page receives some portion of the page rank from other pages, leveraging the damping factor to ensure an overall boost in the network.

• Improving user retention: This would increase the likelihood of a user following internal links indirectly raising the damping factors effect.