Learn to use keyword search terms and apply Boolean logic

Most literature retrieval services are really matchmakers (Table 1.2). They have some provision for searching a subject by way of keywords - brief terms chosen (usually by a study's author) to describe the major topics included in the document. To find the document, one must specify the same keyword that the author has chosen (or a part of it; see "wildcard characters" later in this chapter).

Language gets much of its meaning through context, however. As a result, typing in keywords during an Internet search without specifying their context or relationships can lead to strange, frustrating, or humorous results. To improve the outcome, use a special system called Boolean logic to specify the relationships between search terms.

Boolean logic is named for George Boole, a mathematician who lived in the middle 1800s. It really is justahighbrowed way of describing three logical choices:

I want this one AND that one I want this one OR that one I want this one but NOT that one

Search tools let you apply Boolean logic in various ways. A common variation allows you to choose from a menu of options that describe the Boolean logic, such as "all of these words," "any of these words," and "must not contain."

Suppose you wish to undertake a comparative study of types of skin cancer. By specifying carcinoma AND melanoma, you would retrieve all the hits (entries computer-matched to your search) in which both types of cancers appear in the same document, but none that mention only one. For a comprehensive search on both kinds of skin cancer, you would specify carcinoma OR melanoma. Either or both terms would appear in each document that is retrieved. Alternatively, perhaps you want more information on skin cancers, but know that because of its potential deadliness, there will be hundreds of entries on malignant melanoma. To narrow the results, you could specify carcinoma NOT melanoma. Any document about skin cancer that mentioned melanoma would be omitted from the list of retrievals.

With another system called Implied Boolean, you use "logical operators" - a plus sign in place of AND and a minus sign in place of NOT. The signs abut the front of the word, with no space between them. Precede this with other search terms you want to have it coupled with. For example, type plastic facial +surgery to get results for facial surgery and plastic surgery but not for the words plastic or facial alone. Use a minus sign in front of a word to ensure that a word does not appear in hits. For example, poisoning -food would yield information on poisoning without including entries on food poisoning.

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