The Internet is a vast internetwork of individual computers and computer networks used to share information. Every computer connected to the Internet has a unique Internet Protocol (IP) address. The IP addresses are used to route messages between computers across the Internet and through user networks. Using the IP addresses, any two computers can communicate with one another. In its most basic form, the Internet can be used as a peer-to-peer network. Such a paradigm can be exploited to exchange files between computers, such as File Transport Protocol (FTP) applications. A more common model is the client-server model where web servers store and transmit information, in the form of web pages, to clients upon request. Another application of client-server applications is a newsgroup, where clients can exchange information through a news server.
The Internet, in whatever form, is largely open and unmanaged. Anyone with a computer can connect to the Internet to gather or share information. In addition, any computer can be added to or removed from the Internet at will. Moreover, the information on any given computer can be changed at will. Consequently, the information available on the Internet is extremely fluid.
Because of the Internet's rapidly changing nature, searching for information is limited to viewing snapshots of the Internet. Although many search engines are available to search the Internet, they all suffer from a similar problem. Namely, information found and indexed by a search engine at a particular time may not exist at a later time—when it is needed. Thus, a search engine may report relevant search results but the underlying information may have since been removed from the Internet. A researcher using the search engine can be stymied by stale links to the now nonexistent information.
Eventually, the search engine may purge its database of the old and now nonexistent information. In other words, the search engine may no longer report that the information ever existed. Unless the information reappears, it can be lost forever.