BOOLEAN SEARCHING

BOOLEAN SEARCHING-1st handout

Understanding how to perform sophisticated searches of online information will greatly increase your chances of finding what you want. While most popular search engines let you define your search criteria in very specific ways, not all function identically. Capital Sensitivity If a search keyword is capitalized, the search engine will return only documents containing the capitalized word. For example, if you were interested in documents relating to the country of China, capitalizing the word and using an engine that supports capital sensitivity narrows down the number of results returned, eliminating documents that relate to china dishes or cookery.

Note however, that in many instances it is better to leave keywords uncapitalized to allow the engine to return results that contain keywords in either form. Phrase Searching When using search terms containing more than one word in a specific order, by enclosing the words in quotation marks, the engine returns only documents containing the exact phrase.

Here’s an example: When searching for information on gun control legislation, using “gun control” will eliminate those documents that contain the words gun and control, but not in that order; or even different paragraphs and maybe not even relating to the topic of gun control. Truncation If you are looking for information on gardening, you could use it as your keyword. However, if your results are limited in number (though not likely with gardening) and you want to broaden your search, use a root part of the word and abbreviate it with an asterisk (garden*). The engine will return links to documents containing gardens, garden, gardener, gardeners, and so on. Boolean Logic Perhaps the most useful feature in defining search criteria, Boolean operators provide you with powerful control over search engine logic. The Boolean operators AND, OR, NOT (or AND NOT in some engines), NEAR and parentheses are in many ways analogous to mathematical operators in how they shape the execution of a complex equation. http://kathyschrock.net/rbs3k/boolean/

Here’s what these Boolean operators do for you: AND If you want a document that contains all of your keywords, use the capitalized word AND between keywords. The engine will only find documents that have both words. Here’s an example: Using the search criteria 49ers AND schedule would return all documents that contain both words. Be sure to capitalize all letters in the word AND, otherwise the search engine will treat it as a keyword, not as an operator.

If the left oval represents all documents containing the word 49ers and the right oval represents all documents containing the word schedule, the intersection of those ovals, the green area, represents all documents containing both words. You can see how this operator is useful in narrowing your results. OR If you want to broaden your search to find documents that contain either of the keywords, use the OR operator between words. This is very useful when searching for terms that have synonyms. An example is children OR kids, which would return any document that had either of the words. If the left oval represents all documents containing the word children and right oval represents all documents containing the word kids, the green area represents documents that contain either word or both words. You can see how this operator broadens your search, obtaining more results.

NEAR

This operator is a more specific form of the AND operator. It ensures that the document contains both terms and that they are located near each other. In many lengthy documents, just using the operator AND might not provide useful results as the two keywords may be located in very different parts of the document and might not be related to one another.

NOT or AND NOT

Using the capitalized AND NOT preceding a search term eliminates documents that contain that term. Why would you want to do this? If you want to find information on Eli Manning and do not want documents that include information relating to the New York Giants you could use “Eli Manning” AND NOT New York Giants Parentheses The operators AND, NEAR, OR and AND NOT are powerful in their own right, but when used in conjunction with parentheses, they offer substantial control over the search logic executed by the engine. Parentheses are used in Boolean logic similar to the way they are used in a mathematical equation, limiting and ordering relations between variables. Here’s an example: If you want to find a Web-based Internet tutorial you might use the search criteria Internet AND (tutorial OR lesson). The documents returned must contain both of the words Internet and tutorial or Internet and lesson. Essentially, the parentheses are used as they are for the distribution property in mathematics–to distribute the keyword Internet to either of the two “OR” words inside the symbols. To reiterate: Internet AND (Tutorial OR lesson) would return:

1. Internet and tutorials

2. Internet and lessons

The most common use of parentheses is to enclose two possible keywords separated by an OR operator and then linking those enclosed/possible keywords with other criteria using AND. However, there are times and instances where the reverse arrangement might prove useful.

For example, if you were looking for information on gun control you might want to use “gun control” OR (legislation AND gun), which would return documents with the words “gun control” or documents containing the word gun and the word legislation. Again, to reiterate: “gun control” OR (legislation AND gun),

1. “gun control”

2. gun and legislation.

You can further refine the search. Since the word “law” is a synonym of legislation you can even nest one set of parentheses inside another to distribute gun to either legislation or law and while we’re at it, truncate “law” with an asterisk to also distribute gun to the variation–laws. Here’s how it would look: “gun control” OR (gun AND (law* OR legislation)). Note that each left side parentheses must be paired with a right side one somewhere in the Boolean expression or the search engine will get confused (see how stupid they are!).

To again reiterate: “gun control” OR (gun AND (law* OR legislation) “gun control” gun and law gun and laws gun and legislation +require and -exclude Some engines offer a variation of the Boolean operators AND and NOT. A + symbol preceding a word (with no space between) requires that the word be present in documents. A – symbol preceding a keyword ensures that the word is not present in returned documents. Note that all words that must be in the document should be preceded by a + symbol, even the first word.

Here’s an example: +fraud +election ensures that fraud is also in all the documents. Limited Boolean Options Some engines offer limited Boolean logic with radio buttons or pull-down menu choices such as: Documents must include “All terms” (equivalent to using the operator AND between all terms). Documents must include “Any terms” (equivalent to using OR between all terms).and (see Academic Search Complete (EBSCO) Date Capability Many search engines offer the ability to limit searches by web page creation dates. This is a very useful tool if you are doing continuing research on a specific topic. It enables you to limit the results to pages created since your last search. It is also useful when searching for current event topics.

Note that the implementation of this feature varies widely. Some search engines like Yahoo! offer radio buttons or pull-down menus, while AltaVista and HotBot provide the ability to specify dates or timeframes. Also, date sensitivity is related to the web page creation date, not some historical timeframe.

For instance, it would not be useful to use an engine’s date capability to search for 1907 and information relating to the Wright brothers, since there were no web pages created in 1907! Restricting Searches to Specific Parts of a Document Some engines can limit searches to specific areas, the most common being the document title and URL.

Here’s an example of a title search: If you are looking for information on alternative medicine and believe that there are entire web pages devoted to your subject that have the keywords in the titles, you could use the syntax: title: alternative AND medicine. An example of URL search would be if you are looking for Apple Computer web pages. You could use: url: apple, which would return web pages created by the computer maker Apple (and others). Restricting Searches to Specific Areas of the Web Some engines allow you to limit your searches to “just the Web” or just “newsgroups.” Restricting Searches to Specific Media Popular search engines such as Google, Microsoft Edge, Yahoo! and Firefox allow you to search for various types of media, including audio, video, and graphics. The library at the University of California at Berkeley has an excellent set of charts detailing the features offered by many popular powerful search engines, as well as links to instructions detailing how to use them. http://www.learnthenet.com/english/html/77advanc_3.htm

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