en.wikipedia.org/wiki/Web_search_engine
Search services locate information. Metasearch engines submit search request to several search engine simultaneously. Specialized search engines focus on subject-specific Web sites.
The Web can be an incredible resource providing information on nearly any topic imaginable. are you planning a trip? Writing a economics papers Looking for a movie review. Trying to locate a long- lost friend? Information sources related to these questions,and much,much more are available on the web.With over 2 billion pages and more being added daily. the Web is a massive collection of interrelated pages. With so much available information, locating the precise information you need can be difficult. Fortunately, a number of organizations called search services or search providers operate Web sites that can help you locate the information you need. They maintain huge databases relating to information provided on the Web and the internet. The information stored at these databases includes addresses, content descriptions or classifications, and keywords appearing on Web pages and other Internet informational resources. Special programs called agents, spiders, or bots continually look for new information and update the search services databases. Additionally, search services provide special programs called search engines that you can use to locate specific information on the Web.
- Keyword search: In a keyword search, you enter a keyword or phrase reflecting the information you want. The search engine compares your entry against its its database and returns a list of hits, or sites that contain the key-words. Each hit includes a hyperlink to the referenced Web page (or other resource) along with a brief discussion of the information contained at that location. many searches result in a large number of hits. For example if you were to enter the keyword travel, you would get thousands of hits. Search engines order the hits according to those sites that most likely contain the information requested and present the list to you in that order, usually in groups of 10.
- Directory search: Most search engines also provide a directory or list of categories or topics such as Finance, Health, and News. In a directory search,also kn0wn as an index search, you select a category or topic that fits the information that you want. Another list of subtopicsrelated to the topic you selected appears. You select the subtopic that best relates to your topic and another subtopic list appears. you continue to narrow your search in this manner until a list of Web sites appears. This list corresponds to the hit list previlously discussed.
Figure 2-13
As a rule, if you are searching for general information, use the directory search approach. For example to find general information about music, use a directory search beginning with the category entertainment and then select the subtopic Music. If are searching for spicific information, use the key-word approach. for example,if you were looking for a spicific music file, you would use a keyword search using the album title and or the artist's name. A recent study by the NEC research institute found taht any one search engine includes only a fraction of the informational sources on the Web. Therefore, it is hiighly recommended that you use more than one search engine when researchig importangt topics. See Figure 2-14 for a list of some of the most widely used search engines. Or; you culd use a special type of search engine called a metasearh engine.
Metasearch engines
en.wikipedia.org/wiki/Metasearch_engine
One way to research a topic is to visit the Web sites for several individual search engines. At each site, you would enter the search instructions, wait for the hits to appear, review the list, and visit selected sites. This process can be quite time consuming and duplicate responses from different search engines are inevitable. Metasearch engines offer an alternative.
Metasearch engines are programs that automatically submit your search request to several search engines simultaneously. The metasearch engine receives the results, eliminates duplicates, orders the hits, and then provides the edited list to you. See Figure 2-15for a list of several metasearch engines available on the Web. One of the best Known is MetaCrawler; see Figure 2-16.
SPECIALIZED SEARCH ENGINES
Specialized search engines focus on subject-specific Web sites. Specialized sites can potentially save you time by narrowing your search. For a list of just a few selected specialized search engines,see Figure 2-17. For example, let's say you are researching a paper about the fashion industry. You could begin with a general search engine like yahoo! Or, you could go to a search engine that specializes specifically in fashion such as infomat.com.
