What is PageRank

Google sorts the search results using their own PageRank algorithm. Each site is assigned a number based on the number of links from other pages that point to the value of those pages, and other non-public criteria.

PageRank was made a trademark and patentada1 by Google on January 9th 1999 that covers a family of algorithms used for assigning numerical relevance of the documents (or web pages) indexed by a search engine.

Its properties are much discussed by the experts in search engine optimization. The PageRank system is used by the popular search engine Google to help determine the importance or relevance of a page. It was developed by Google founders Larry Page and Sergey Brin at Stanford University.

PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of the value of a particular page. Google interprets a link from page A to page B as a vote, by page A, for page B. But Google looks beyond the volume of votes, or links a page receives and also analyzes the page that casts the vote.

Votes cast by pages considered “important”, i.e. with a high PageRank are worth more, and help to make other pages “important.” Therefore, the PageRank of a page reflects the importance of it online. The initial PageRank algorithm can be found in the original document where its creators introduced the prototype of Google: “The Anatomy of a Large-Scale Hypertextual Web Search Engine.”

Where:
PR (A) is the PageRank of page A.
d is a damping factor that has a value between 0 and 1.
PR (i) are the PageRank values with each of the pages linking to Ai.
C (i) is the total number of outbound links on page i (whether or not to A);
Some experts say the value of the variable d is usually 0,85.3 representing the probability that a surfer continues clicking links while surfing the Net instead of typing a url directly into the address bar or click one of the bookmarks and a value set by Google.

Therefore, the likelihood that users stop pressing the links and navigate directly to another random site is 1-d. The introduction of the damping factor in the formula subtracts some weight to all websites. If a user lands on a page without links, which will be navigate to any page at random, it is equivalent to assuming that a page with no outgoing links has links to all websites.

The weight or importance of a page is the result of a “ballot” among all other pages on the World Wide Web about the level of importance of that page. A hyperlink to a page counts as a vote of support. The PageRank of a page is defined recursively and depends on the number and PageRank of all pages that link has.

A page that is linked by many pages with high PageRank also gets a high PageRank. If there are no links to a web page, there is no support for that specific page. The PageRank of the Google toolbar is from 0 to 10.

Ten is the maximum possible PageRank and very few sites have this rating, 1 is the minimum qualification you receive as a regular site, and zero means that the site has been penalized or not yet received a rating of PageRank. It seems to be a logarithmic scale. The exact details of this scale are unknown. An alternative to the PageRank algorithm proposed by Jon Kleinberg, is the HITS algorithm.

Handling

Due to the commercial importance of the top search engine results, they have developed methods to artificially manipulate the PageRank of a page. These methods should be pointed out as spam, to add links to a certain web page in places like blogs, guestbooks, forums, websites etc. with the intention of increasing the number of links pointing to the page.

In early 2005, Google implemented a new attribute for hyperlinks rel = “nofollow” as an attempt to combat spam. Thus when calculating the weight of a page, it does not take into account the links that have been attributed.

Background

PageRank has taken its model from the Science Citation Index (SCI) developed by Eugene Garfield Institute for Scientific Information (ISI) in the U.S during the 50s. The Science Citation Index is intended to resolve the allocation objective scientific merits assuming that researchers whose impact factors (number of publications and/or references in other scientific papers) is higher, collaborating further with the development of the research area.

The citation index is a crucial element to select which researchers receive scholarships and research resources.