|“||A search engine will find all web pages on the Internet with a particular word or phrase. Given the current state of search engine technology, that search will often produce a list of hundreds of web sites through which the user must sort in order to find what he or she is looking for.||”|
How it works
A search engine starts with a list of one or more websites. The engine then requests the home page from each site on its list. When a home page is retrieved that has links to yet other pages, the search engine requests a copy of each of those pages that these links point to. And if those pages in turn contain links to yet more pages, the search software requests a copy of those pages. And so on, day after day, ceaselessly.
At its most basic level, a search engine maintains a list, for every word, of all known Web pages containing that word. The collection of lists is known as an "keyword index." Search engines vary according to the size of the index, the frequency of updating the index, the search options, the speed of returning a result, the relevancy of the results, and the overall ease of use. No two search engines work the same way.
In practice, most search engines do not exhaustively cover all possible websites. In addition, some search engines pass along material for review by human editors, who rate the pages retrieved on a variety of scales — quality, appropriateness for families, and so on. The creation of such an annotated index obviously takes longer than it does to create a comparable unannotated index. Search engines are the primary means by which Internet users can find digital information. However, it must be remembered that a search engine is NOT searching the Internet as it exists at the time of the search, but is only searching the search engine's database, which may be days or weeks out of date at any given point in time.
Search engines regularly return to the web pages they have indexed to look for changes. When changes occur, the database is updated to reflect the new information. However, the process of updating can take a while, depending upon how often the search engine makes it rounds and then, how promptly the information it gathers is added to the database. Until a page has been both spidered and indexed, the new information will not be available. Thus, the more often a search engine checks for changes, the more accurate its search results will be.
The accuracy of search results is directly proportional to how many web pages the search engine indexes. The more web pages the search engine indexes, the more accurate and complete will be the search results. The accuracy of the search results also depends on how often the search engine indexes web pages. The more often the search engine indexes the web pages, the more accurate the search results will be.