A search engine lists web pages on the Internet. This facilitates research by offering an immediate variety of applicable options. Possibly useful items on the results list include the source material or the electronic tools that a web site can provide, such as a dictionary, but the list itself, as a whole, can also indicate important information, perhaps inasmuch as a book can be judged by its title. The advantages of a specific search engine can be distinguished by using a variety of common search engines. The distinct advantages of each are their user interface and, less obviously, their algorithms for compiling and searching their own indexes. Because a web crawler can be blocked—specific ones or just in general—different search engines can list different web sites, and there are more web sites available by URL than are indexed in any database.
Search engines cannot:
- Guarantee the results are reliable or "true" (search engines index whatever text people choose to put online, true or false).
- Guarantee why something is mentioned a lot, and that it isn't due to marketing, reposting as an internet meme,spamming, or self-promotion, rather than importance.
- Guarantee that the results reflect the uses you mean, rather than other uses. (E.g., a search for a specific John Smith may pick up many "John Smiths" who aren't the one meant, many pages containing "John" and "Smith" separately, and also miss out all the useful references indexed under "J. Smith" or, if the term is put in quotes, "John Michael Smith" and "Smith, John")
- Guarantee you aren't missing crucial references through choice of search expression.
- Guarantee that little-mentioned or unmentioned items are automatically unimportant.
- Guarantee that a particular result is the original instance of a piece of text and not a reprint, excerpt, quotation, misquotation, or copyright violation.
and search engines often will not:
- Provide the latest research in depth to the same extent as journals and books, for rapidly developing subjects.
- Be neutral.
A search engine test cannot help you avoid the work of interpreting your results and deciding what they really show. Appearance in an index alone is not usually proof of anything.
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