Chapter 3 Searching the Web - Search Tools

Specialized Web based search tools are used to locate Web pages, businesses, people, multimedia files, documents, databases, and more.  The three main search tools are directories, search engines, and metasearch engines.  Directories are a human-compiled hierarchical list of Web pages organized by category.  You can drill down the directory categories by clicking a number of links to move from a general category through additional subcategories, to the main Web page line, and finally to the main Web site.  

Search engines help to enable users to research the directory's index by keywords instead of drilling down through categories and subcategories.  They include general-purpose search tools, such as Google, and use software called a Web crawler that browses the Web automatically adding the URL's and other information about Web pages to a searchable index.  The Web page information retrieved by a Web crawler is stored in a database on one or more servers.  This creates an index.  The search engine compares the keywords with its index and complies a list of Web pages for which the keywords are relevant and arranges the list in a specific order.

The third main search tool, metasearch engine, is a special type of search tool that compiles the search results from multiple search engines into a single search results list.  This allows one to perform multiple search engines at once.  Examples of metasearch engines are MetaCrawler, Dogpile, KartOO, and Ixquick.  A good metasearch engine should eliminate duplicate entries, categorize the hits based on topic, order the hits by relevance, and indicate which search engines provided the search results.