Grand Valley State University Imagine a library containing 25
billion documents but with no centralized organization and no
librarians. In addition, anyone may add a document at any time without
telling anyone. You may feel sure that one of the documents contained in
the collection has a piece of information that is vitally important to
you, and, being impatient like most of us, you'd like to find it in a
matter of seconds. How would you go about doing it? Posed in this way,
the problem seems impossible. Yet this description is not too different
from the World Wide Web, a huge, highly-disorganized collection of
documents in many different formats. Of course, we're all familiar with
search engines (perhaps you found this article using one) so we know
that there is a solution. This article will describe Google's PageRank
algorithm and how it returns pages from the web's collection of 25
billion documents that match search criteria so well that "google" has
become a widely used verb. Most search engines, including
Google, continually run an army of computer programs that retrieve pages
from the web, index the words in each document, and store this
information in an efficient format. Each time a user asks for a web
search using a search phrase, such as "search engine," the search engine
determines all the pages on the web that contains the words in the
search
