Internet Search Engines
An Internet searcj engine is an application , which helps users locate web sites containing useful information and references to such information on the WWW. To search information on the WWW, a user types the description of the information using the user interface of the search engine. The search engine then searches the requested information on the WWW and returns the results to the user. The results enables the user to locate the requested information quickly from the vast ocean of information availbale on the Internet.
Major Elements of Internet Search Engines
Three major elements of an Internet search engine are as follows:
1.Search request Interface - enables users to provide description of desired information to the search engine. Depending on the comlexity of this element, the search engine may allow specifications of simple keywords and phrases, combination of keywords and phrases using Boolean operators and exclusion/inclusion operators, and titles and URL limiters.
2. Information discoverer :- discovers information from the WWW and creates a database for the search engine. The search engine uses the database to locate useful information during the search process. Information discoverer accrues this information in two-ways:
(a) In manual method:- authors provide information about their websites to the search engine;
(b) In automatic method:- information discoverer collects the information using programs, such as web crawlers , spiders, robots. These programs periodiacally roam on the Internet, and store links of information using programs such as web crawlers , spiders , robots. These programs periodically roam on the Internet, and store links of information about each page they visit along with their associated hyperlinks, information discoverer then creaters an index form the results of automated search . If a web page owner updates his/her web page. the spider finds these changes and updates its index.
3. Presenter of search results : returns search results, ranking them in an order it believes, is most relevant ot the search . Search engines often list search results in accordance to a relevance score. Relevance scores reflect the number of times a search term appears in a web page. Some search engines also allow users to control relevance score by giving different weights to each search word.
Some Popular Internet Search Engines
Today, there are more than two dozen major search engines available on the WWW. Some Popular ones are:
1. Google(www.google.com)
2. Yahoo(www.yahoo.com)
3. Bing (www.bing.com)
3. HotBot(www.hotbot.com)
4. Lycos(www.lycos.com)
5. Inference Find(www.infind.com)
