Google的技术剖析：创始人Sergey Brin 和 Lawrence Page的研究论文

2.1 PageRank: Bringing Order to the WebThe citation (link) graph of the web is an important resource that has largely gone unused in existing web search engines. We have created maps containing as many as 518 million of these hyperlinks, a significant sample of the total. These maps allow rapid calculation of a web page@#s "PageRank", an objective measure of its citation importance that corresponds well with people@#s subjective idea of importance. Because of this correspondence, PageRank is an excellent way to prioritize the results of web keyword searches. For most popular subjects, a simple text matching search that is restricted to web page titles performs admirably when PageRank prioritizes the results (demo available at google.stanford.edu). For the type of full text searches in the main Google system, PageRank also helps a great deal.

2.1.1 Description of PageRank CalculationAcademic citation literature has been applied to the web, largely by counting citations or backlinks to a given page. This gives some approximation of a page@#s importance or quality. PageRank extends this idea by not counting links from all pages equally, and by normalizing by the number of links on a page. PageRank is defined as follows: