A search engine is a program designed to help one access files
stored on a computer, for example a public server on the World Wide Web.
The search engine allows one to ask for media content meeting specific
criteria (typically those containing a given word or phrase)
and retrieving a
list of files that match those criteria. Unlike an index document that
organizes files in a predetermined way, a search engine looks for files
only after the user has entered search
criteria.In the context of the Internet, search engines
usually refer to the World Wide Web and not other protocols or areas.
Furthermore search engines mine data available in newsgroups, large
databases, or open directories like DMOZ.org. Because the data
collection is automated, they are distinguished from Web
directories, which are maintained by people.The vast majority of
search engine are run by
private companies using proprietary algorithms and closed databases,
the most popular currently being Google
(with MSN Search and Yahoo!
closely behind).
There have been several attempts to create open-source
search engines, among which are Htdig,
Nutch, Egothor
and OpenFTS.
[1]
(http://www.searchtools.com/tools/tools-opensource.html)
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