Because there are so many different ways of organizing and indexing the information found on web pages, no one directory or search engine can be clearly identified as the best to use for all searches. Often, one of the best strategies for a successful search is to use several different search engines in order to cover the subject thoroughly. Repeat these searches using several similar but significantly different sets of keywords. Because of the advantages of searching multiple engines, several "meta-searchers," search engines that can pass keywords to multiple directories and indices at once, have been developed. One such search engine is the MetaCrawler developed by Erik Selberg and Oren Etzioni at the University of Washington.

MetaCrawler passes your query on to nine separate search engines including Alta Vista, Yahoo, Open Text, and Lycos. As each engine returns its results MetaCrawler organizes the results, removing redundant entries and displaying them in a uniform format. MetaCrawler has advanced Boolean search capabilities and uses the same, + and - sign operators as Alta Vista (see preceding section of this lesson). In addition, below the search entry blank on the MetaCrawler search page are three buttons. The "All words" button is equivalent to using the AND Boolean operator. The "Any words" button is equivalent to using OR. The third button, "As a phrase," restricts the results to only sites that have an exact sequential match for the words you entered. It is equivalent to putting quotes around all your words in an Alta Vista search.

Considering the advantages of being able to search multiple engines at once, you may be wondering. "why not just use meta-searchers all the time?" The reason for continuing to use single index searches is simple. The search engine for a single index, like Alta Vista, is specially designed for its index, making it faster and more accurate. Single index engines also often include additional Boolean options not available in more generic meta-searchers, and how even simple operations are applied to a search can be customized to make best use of how the index is formed. Further, meta-searchers only return the top of the list created by each search engine (the top 10 from each is common) whereas, in individual search engines you are able to look at more entries that the original ones returned as "most likely" candidates. In many instances, using a meta-searcher may be all that is needed to find the information for which you are looking, but other times the best use of the meta-searcher is to discover which search engines appear to be best suited for your set of keywords. Often times, the top three or four possibilities from a meta-search will be from a single search engine, and that may be a sign to try that engine next if you don't find exactly the information you want.

Using the same keywords you used in the Alta Vista search you did in the preceding section, try a search at MetaCrawler
Consider how the results differed and look through the list to see if any new sites were found by other search engines that might contain information on your topic.