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Section: Search Tools

Main Categories of Search Tools

General Search Engines

  • Return webpages containing specified keyword(s) or phrases contained in the title or content of the webpage.
  • Retrieve webpages that have been indexed (or crawled) by WWW robots or spiders and added to the search engine's searchable database.
  • Each general search engine allows you to search a different subset of the WWW; however, you will see significant overlap in results lists for identical searches using different engines.
  • Since each engine only searches a portion of the WWW, using more than one search engine is recommended for research purposes.  Google provides access to the largest amount of Web content.  Therefore, it is recommended that you use Google and one other General Search Engine for research purposes on the publicly accessible WWW.

Examples of General Search Engines: Google, Yahoo! Search, Ask Jeeves, Teoma

Subject Directories

  • Collections of world wide web resources chosen by site creators or evaluators.
  • Arranged by a subject or classification scheme. Navigation from broader to more specific topics.
  • Can deal with a broad range of topics or a narrow subject area.
  • Human selection is required for inclusion. Content is not indexed (or crawled) by WWW robots or spiders; rather, a person has made a conscious decision to include the site in a Subject Directory.  Therefore, Subject Directories tend to provide access to a much smaller subset of the WWW than other types of search tools.
  • Human selection provides an initial filter for quality control.

Examples of Subject Directories: Infomine, Academic Info, Canadian Information by Subject

Invisible Web Search Engines

  • Invisible Web is estimated to be 2-3 times larger than the visible Web.  It contains content that most General Search Engines cannot access or for which links cannot be generated.  A record for a book in the York University Libraries catalogue is part of the Invisible Web.
  • Searches for items in the Invisible Web that most search engines will not or cannot index for searching or finds database-specific search tools (e.g., York University Library Catalogue) that provide access to Web content.
  • Invisible Web search tools can be publicly accessible (e.g. the Internet Movie Database, York University Library Catalogue) or subscription-based (e.g., Scholars Portal, Expanded Academic).
  • Individual databases in the Invisible Web each deal with particular kinds of content (e.g., citations to articles in a particular subject area, information about movies).

Examples of Invisible Web Search Engines: Invisible Web Directory, Direct Search

Meta-Search Engines

  • These search engines submit your search to several General Search Engines simultaneously. Number of results and coverage of the WWW is entirely dependent upon which search engines are used by an individual meta-search engine.

Examples of Meta-Search Engines: Dogpile, Mamma, Vivisimo


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