PageRank – What Is It?

The PageRank algorithm is one used for link analysis. Within a set of hyperlinked documents, like the World Wide Web, its purpose is to weigh each document’s importance by assigning to it a numerical value. The application of the algorithm can be extended to any set of things linked reciprocally, by quotes or references. It is used as the basis for all of Google’s web search tools, but only partly contributes to the ranking of a page in the Google search engine’s list of results.

Created at Stanford University, PageRank got its name from its creator, and part owner of Google, Larry Page. The algorithm has been patented and the name is a trademark of Google. Stanford University has the patent assigned to it, but for the price of 1.8 million of Google’s shares, the university have given Google the exclusive license rights to the patent.

The algorithm works by assigning importance to a page, a rank value, which is a function of the rank values of all the pages that link to it. A page that is linked to by a lot of pages with high PageRank, itself has a high PageRank. Essentially the algorithm is a probability distribution that represents how likely it is that a person who is randomly clicking on links, will arrive at a certain page.

There are problems with this process concerning its being manipulated, and this has drawn much academic attention throughout PageRank’s lifespan. Ways of finding and excluding pages from the process who’s PageRanks are increased artificially have been the focus of intense research. There have been cases where companies sell to webmasters links with high ranks. This has been publicly condemned by Google, who warns that such dishonest attempts to increase a pages rank will result in the relevant pages being ignored from the PageRank process.

Other areas of thought and analysis have benefited from PageRank, some of which are ecology, ranking the importance of certain animals to the flourishing of an environment; and such computational linguistics issues as word sense disambiguation. Although it was only developed a few decades ago, PageRank’s relevance to our modes of analysis in is growing.

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