Search engine (computing)

The phenomenal success of the Google search engine was mainly due to its powerful Pagerank algorithm and its simple, easy-to-use interface.

A search engine is a program designed to help find files stored on a computer, for example a public server on the World Wide Web, or one's own computer. 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. A search engine often uses a previously made, and regularly updated index to look for files 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]

History

The first Web search engine was "Wandex", a now-defunct index collected by the World Wide Web Wanderer, a web crawler developed by Matthew Gray at MIT in 1993. Another very early search engine, Aliweb, also appeared in 1993 and still runs today. One of the first engines to later become a major commercial endeavor was Lycos, which started at Carnegie Mellon University as a research project in 1994.

Soon after, many search engines appeared and vied for popularity. These included WebCrawler, Hotbot, Excite, Infoseek, Inktomi, and AltaVista. In some ways they competed with popular directories such as Yahoo!. Later, the directories integrated or added on search engine technology for greater functionality.

In 2002, Yahoo! acquired Inktomi and in 2003, Yahoo! acquired Overture, which owned AlltheWeb and Altavista. In 2004, Yahoo! launched its own search engine based on the combined technologies of its acquisitions and providing a service that gave pre-eminence to the Web search engine over the directory.

In December 2003, Orase published the first version of its new real-time search technology. It came with many new functions and the performance increase a lot.

Search engines were also known as some of the brightest stars in the Internet investing frenzy that occurred in the late 1990s. Several companies entered the market spectacularly, recording record gains during their initial public offerings. Some have completely taken off their public search engine, and are marketing Enterprise-only editions, such as Northern Light which use to be part of the 8 or 9 early search engines after Lycos came out.

Before the advent of the Web, there were search engines for other protocols or uses, such as the Archie search engine for anonymous FTP sites and the Veronica search engine for the Gopher protocol.

Osmar R. Zaïane's From Resource Discovery to Knowledge Discovery on the Internet details the history of search engine technology prior to the emergence of Google.

Recent additions to the list of search engines include a9.com, AlltheWeb, Ask Jeeves, Clusty, Gigablast, Ez2Find, Teoma, WiseNut, GoHook, Walhello and Kartoo.

Google

Around 2001, the Google search engine rose to prominence. Its success was based in part on the concept of link popularity and PageRank. How many other web sites and web pages link to a given page is taken into consideration with PageRank, on the premise that good or desirable pages are linked to more than others. The PageRank of linking pages and the number of links on these pages contribute to the PageRank of the linked page. This makes it possible for Google to order its results by how many web sites link to each found page. Google's minimalist user interface was very popular with users, and has since spawned a number of imitators.

Researchers at NEC Research Institute claim to have improved upon Google's patented PageRank technology by using web crawlers to find "communities" of websites. Instead of ranking pages, this technology uses an algorithm that follows links on a webpage to find other pages that link back to the first one and so on from page to page. The algorithm "remembers" where it has been and indexes the number of cross-links and relates these into groupings. In this way virtual communities of webpages are found.

Challenges faced by search engines

• The web is growing much faster than any present-technology search engine can possibly index (see distributed web crawling).
• Many web pages are updated frequently, which forces the search engine to revisit them periodically.
• The queries one can make are currently limited to searching for key words, which may results in many false positives.
• Dynamically generated sites, which may be slow or difficult to index, or may result in excessive results from a single site.
• Many dynamically generated sites are not indexable by search engines; this phenomenon is known as the invisible web.
• Some search engines do not order the results by relevance, but rather according to how much money the sites have paid them.
• Some sites use tricks to manipulate the search engine to display them as the first result returned for some keywords. This can lead to some search results being polluted, with more relevant links being pushed down in the result list.

See also

• Search engine spammer
• History of the Internet
• List of search engines
• Data mining
• Metasearch engine

External links

• Articles and information on search engines and how they work
• On Search, the Series; Tim Bray; 2003 — A series of essays on search engine techniques.
• Search engine makes social calls (March 7, 2002; Nature.com)
• searchtools.com, a comprehensive list of free and commercial seach software