Sergey Brin and Larry Page, the inventors of PageRank, began with a simple summation equation, the roots of which actually derive bibliometrics research, the analysis of the citation structure among academic papers.
The standard conceptual model of PageRank is called the random surfer model. Consider a surfer who starts at a web page and picks one of the links on that page at random. On loading the next page, this process is repeated.
PageRank idea is that for a web page to be considered important there must be a large number of other web pages linking to it. The page has high rank if the sum of the ranks of its incoming link, recursively is high. These linking web pages must be sufficiently important themselves, and the number of other web pages to which they link must not be too large.
A difficulty to the PageRank method is that some web pages do not link to any other web page. Web pages without outgoing links are referred to as dangling modes in the PageRank literature. The most common way to deal with dangling nodes is to create artificial links from each dangling node to all other web pages.
What is PageRank?
