Internet Search Engines | ||
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Search engines are commonly used to find information on the Internet. They rely on sets of protocols to search a database of websites compiled by Web roaming search bots (software robots) called spiders or crawlers. Originally these bots searched all fields of an HTML Web page. However, with the explosive growth of the Internet, most bots now only search a few fields. More and more search bots have to restrict themselves to the "meta tags" in which authors have listed relevant keywords. If a site meets collection criteria, it is indexed and added to the database. Consequently, each search engine has it's own set of collected sites. None of the collections cover the entire Web. In fact, even the best collection represents less than 20 % of the Web. The search engine's bots constantly update the indexed collection of websites. To find out more about how each search engine operates, check each site's "about us" button. The following chart compares how various search engines operate:
Common FeaturesBelow are several features common to both subject directories and search engines:
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Sample SearchLet's return to our male breast cancer search terms and see what we get using different search engines. We will start with Alta Vista, one of the commonly used engines. After entering our search terms into the box and pressing the "Search" button, we get the following listing: | ||
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As you'll notice from this example, the list of Web pages is ranked. Commercial search engines as well as subject directories have "featured" sites that have paid to be "found" at the top of the list. A brief description of the page is often included. For comparison purposes, let's try the same search using another popular search engine, Google. Entering our search term male breast cancer, we get back these results: | ||
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Although Google returned fewer results than Alta Vista, it still came back with an unmanageable number of 271,000. At least Google labels the links paid for by a sponsoring organization. In comparing Alta Vista's and Google's results, we can see that the first link is the same, but many of the following links are different. Let's go back to ALLTHEWEB Search and see what we get for male breast cancer. | ||
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Even though we're down to 3,931 sites found, we still have quite a number to shift through. Again, some websites found by ALLTHEWEB search are the same as Alta Vista and Google, while others are different. When searching the Web, it's a good idea to try several different search engines and/or subject directories. Searching techniquesUsing a search engine is a good way to look for information on the Web. However, as we just discovered, you may get LARGE numbers of results unless you refine your search. Here are some common techniques you might find helpful. Boolean OperatorsRemember our old friends the Boolean Operators? We first discussed them in the section, "Beginning your Research." If you don't remember, here's a quick review of using operators AND, OR and NOT: AND (+) - when using this operator, the search results will show both or all terms on a page in any order (This may or may not be the default search pattern.) OR - when using this operator, the search results will show either or any of the terms on a page. This is a broad searching technique which usually results in a large set of results. (May be the default operator for a search engine.) AND NOT (-) - when using operator, any page with the term after the operator is eliminated from the results. This can help narrow your search. Additional operators may be used. You'll need to check the advanced features on the particular search engine or directory to be sure. For a quick overview of several popular search engines, click on http://lisWeb.curtin.edu.au/staff/gwpersonal/compare.html. Returning to ALLTHEWEB Search, we can see how some of these advanced features work: | ||
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Let's fill the fields as follows: | ||
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When we do a search based on the above terms we get more manageable results: | ||
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Phrases (Multiple terms)Some search engines now default to a phrase search if multiple words are entered. However, not all search engines will correctly understand a phrase. To make sure you get the phrase you want, use quotation marks " " around the phrase. For example, use "breast cancer" instead of just breast cancer. When in doubt, check the help or advance features menu. If you forget the quotation marks, the terms may be read as independent words. Search results will be much larger if the engine is looking for the word breast and the word cancer on the same page versus the phrase breast cancer. The result of "breast cancer" is a search for a specific kind of cancer. With some search engines, capitalization is recognized. The American Cancer Society may be searched as a phrase because of the capitalization. However, this phrasing isn't implemented in every search engine. To be sure, make it a phrase by using quotation marks. TruncationSome engines accept wild card characters for variations of a word, for plurals and truncation. Some automatically search for singular or plural. Check the help screens for special features. | ||
Meta Search EnginesSeveral search engines do a global or multi-site search. Meta Search engines search the indexes of several different search engine sites at once. Each meta engine has a different set of search engines they cover. Each time you enter a search statement, they execute the search in each search engine before returning the results. Some will strip out duplicate pages and combine the result into one listing. Meta searches are useful when you have a simple term you need to find. Remember, because search engines are different, you may eliminate some of them if your search is complicated and has too many special limits. It may take longer to search. Check the help screens for specific details. | ||
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Online Resources:Commonly used search engines:
Meta Search EnginesAll-in-One Search Strategies
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