About Search Engines and Indexes.
author: cwis.admin@unh.edu

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A number of major search indexes exist for finding things on the Internet. Each has its own "personality" in terms of what is indexed, how keyword searches may be specified, how much information is returned, and speed of response.

In the Internet jargon these indexes are often called "search engines" in reference to the discovery (spidering), indexing, and retrieval software on which they are built. Sometimes other terms such as "information discovery" are used. Typically you enter keyword(s), they return matches as hyperlinks, and you select interesting-looking hyperlinks to go directly to the resource. A reasonable strategy is to try each engine a few times to find the one or two that most often meet your needs. If you use an index repeatedly it is a good idea to read about the details of its search syntax so you can most effectively specify your searches.

The indexes listed here are those that aim, to varying degrees, at indexing broad categories of information. There is an inherent tension between wide discovery of information and narrow retrieval of limited relevant matches from that wider body of information. We can distinguish some services, such as Yahoo, that are more properly called directory services than search engines. They are based on a limited body of information selected for relevance (or tie-in to paying advertisers!). The distinction between these directories and search engines is blurred because the major directories are setup to seamlessly kick-over to a wider search engine if there are no matches in their core collection. Several well-known search services do not operate their own discovery and indexing operations, but buy that service and then package it with their own front end Web pages. Inktomi, for example, supplies such services to HotBot and Yahoo.

If you aren't sure where to begin, take a look at Google and Yahoo!

A newer category of search index is the "metasearch". These take your search text (phrase or keywords) and then send them to multiple search engines and tools for you. They vary widely in how they work. The tradeoffs for this tantalizing one-stop shopping are learning to use it effectively, possible time-delays when the Internet is busy, and potential information overload. If you want to try one, look at Metacrawler.