Search engines, directories, and indexes are automated computer programs which use various forms of artificial intelligence to seek out and retrieve website information related to a specific topic or concept phrase, entered by the computer-user in a search-query dialog box of a Web browser (e.g., Netscape, Mosaic, Lynx, Microsoft Internet Explorer, etc.).
A search engine, unlike a directory, maintains its database of sites by using automated software programs called spiders, bots, or webcrawlers to wander the Web in search of information. Search engine databases (e.g., AltaVista or Fast Search) are typically much larger than those of directories (e.g.,Yahoo!) because spiders/webcrawlers can bring back to the database large quantities of retrieved information in a relatively short time.
Many search programs employ Boolean logic, expanding or limiting a search by including connecting terms-- e.g., AND, OR, NOT. The more precise the query, the better the retrieved results.
Boolean search symbols for some web resources:
The query produces a retrieved list of Web sources ranked in a pre-determined order (relevance ranked). Most, but not all, search engines operate in a similar manner, yet rarely return the same results. Not all hits (items retrieved) will be relevant to the intended topic or keyword search. To increase the breadth and depth of a search, change search engines frequently and run search again, comparing retrieved results carefully.
(HINT: Not every web page available on the web in included in any ONE search engine, index, or directory. The web is just too massive and currently contains hundreds of millions of web pages. Change to a different search tool if you can't find what you want after a few tries.)
Complementing search engines are directories and indexes, which are searchable hierarchical databases, sometimes created by human input, where a user can browse by subject categories, much like searching the index in the back of a book. Broad subject areas, like sports or entertainment, are narrowed into specific subcategorizes, as you might find when the searching the Yellow Pages directory. Directories are sometimes called subject trees or catalogs. The differences between search engines and directories or indexes are merging as each absorbs the attributes of the other.
© Copyright 2000 Bonnie Stephenson, MLIS
Saddleback College Librarian