Dr. Write's Infirmary Pages / Research

Some Notes on Boolean Searches

Computer output depends upon human input; it's only as useful as the instructions you provide. Access to computer databases is more available to the average person. You can locate a variety of materials in a wide range of disciplines by using computerized search mechanisms (called "search engines") which are based on Boolean logic. Boolean logic is a form of algebra for performing operations on "sets." If you understand the way Boolean operators manipulate topics and can picture compound subject headings, you can enter precise and logical search statements and reduce your search time and improve your results.

AND, OR, and NOT

The principal Boolean Operators are AND, OR, and NOT. In a Boolean search strategy, AND, OR, and NOT, are used to create a compound subject by combining topics. These three Operators perform different functions even when they are used to relate the same two topics.

AND

OR
The OR operator is often used when an idea can be expressed by synonyms in order to broaden the search. OR links two terms and expands a search. For example, if you search for "Cars or Autos," articles in which either term appears will be retrieved .

OR is very useful because writers and researchers often use different words that have approximately the same meaning. For example, articles about middle and high school students may refer to them as teenagers (teens), adolescents, or youths, so you would want to search for all three: teenagers OR adolescents OR youths. "OR" can also be very useful when there are many synonyms for a concept, and you don't know which one might have been chosen by the author or indexer. For example, teenagers OR adolescents OR youth will yield many more citations than any of these words by itself.

NOT
The first term in the earlier search statement "Spirits AND Fraternities" could result in citations to articles about supernatural beings or moonshine. This type of linguistic problem can be avoided by using the NOT operator to restrict the search. "Spirits NOT Alcohol" will exclude data on spirits which are bottled and not ethereal. Some search engines use a minus sign (-) for the NOT function.

Use NOT to eliminate a term from the search strategy; each document must not contain the term following NOT. NOT narrows a search by excluding articles containing the second search term. For example, if you search for "Virus not AIDS," all articles in which "Virus" appears will be retrieved except for those also containing the word "AIDS."

Combining Operators

The best searches combine the operators. Consider the search statement: "Spirits AND Fraternities NOT Alcohol." This search statement will find information on hauntings at fraternities, while excluding other varieties of spirits. Likewise, a search statement that searches ROCK and ROLL, but not BEATLES will yield all rock and roll articles, but eliminate those that mention the Beatles.

Before you Begin Your Search

Before beginning a search you should identify the words and phrases which will elicit the best or most appropriate sources. What are some synonyms for your topic? Where will you search? To avoid wasting valuable time, consider thoughtfully which search technique is likely to produce the most useful results.

Internet Searches

Netscape provides a variety of search "engines." Each has its own peculiar set of conventions, but they all adhere to the standard boolean search logic. Here's a brief rundown of two which seem to provide the most options and come up with the best responses.

ALTA VISTA
Alta Vista offers "Simple Queries" and "Advanced Queries," but they are simply different interfaces to the same search engine so, under certain conditions, apparently identical queries can produce slightly different results, depending on whether you submit them as Simple or Advanced Queries. In each type of search, the results are listed in order of "rank."

For example, submit PLATO as a one-word Simple Query and then as an Advanced Query, but with no ranking specified (plato is in the search field and nothing is in the ranking field.) Each of the two queries produces "about 20000" documents, but the ranking is different in each case. This is because a Simple Query gets transformed into a boolean expression together with a set of words to rank the results.

For Simple Queries Here's some of the basics for simple searches in Alta Vista:

A search for PARIS "petite galerie" louvre finds documents containing as many of these words and phrases as possible, ranked so that documents with the most matches are presented first. (A phrase is any string of adjacent words.) The preferred way to link words into a phrase is to use quotes.
A lower-case search will also find matches of capitalized words. For example, paris will find matches for paris, Paris, and PARIS.
Capital letters in a search force an exact case match on the entire word. For example, submitting a query for parIS will search only for matches of parIS.
Matches may be required, or prohibited. Precede a required word or phrase with + and a prohibited one
with -. +noir +film -"pinot noir" finds documents containing film and noir, but not containing pinot noir.
Punctuation glues words into a phrase, just as quotes do. Punctuation is treated as white space, so antique;pump;organ is equivalent to "antique pump organ" (that is, three words enclosed in quotes).
quilt* matches pages that contain at least one word such as quilt, quilts, quilting, quilted, quilter etc. (Hint: The *-notation is also useful for searching for variant spellings. For example, alumi*m will find matches for both aluminum and the British English aluminium.)

Advanced Queries
Advanced Queries use operators and expression syntax to construct queries. The rules for defining words and phrases, capitalization and wildcards are, however, the same as for Simple Queries.

You must use the binary operators AND, OR, NEAR, and the unary operator NOT to combine words and phrases.
The operators can also be written in lower-case: and, or, not, near. Alternatively, you can use the symbols & for AND, | for OR, ! for NOT, and ~ for NEAR.
If you need to use any of these words as search words in a query, you must place them in quotes.
You are allowed to use parentheses to group search expressions; in fact it's recommended as less confusing.

Using the operators AND, OR, NEAR, and NOT
A search for kayak AND "San Juan Islands" ensures that both items are present in the resulting documents. The operator AND binds less tightly than juxtaposition.

In a search for "Digital Equipment Corporation" OR DEC, OR ensures that at least one is present in the resulting documents. The operator OR binds less tightly than the operator AND.
In a search for Louis NEAR Monier, NEAR ensures that both are within ten words of each other in the resulting documents. The operator NEAR binds less tightly than the operator NOT and associates to the left. (This query looks for Louis Monier, Louis M. Monier and Monier, Louis.)
In a search for vegetable AND NOT "brussel sprouts" the operator NOT is used to exclude words or phrases from a query. The operator NOT binds less tightly than the operator OR

INFOSEEK
Here are some tips for refining the InfoSeek search:

Capitalize names of people and places
Use a comma to separate lists of names.
To identify a group of words that must appear together in order, use double quotation marks around them, or hyphenate them.
To find proper names, capitalize them ("December" and "California.") If you capitalize adjacent names, Infoseek Guide treats the words as a single name. For example, to find sites that mention the actress Rain Phoenix, type: Rain Phoenix If you don't capitalize a proper name, it is treated like any other word. Typing rain phoenix finds sites about weather and Phoenix (AZ), rather than information about River's sister.
If you want to search for several names, use commas to separate the different names. For example, to search for Babe Ruth and the Boston Red Sox, type: Babe Ruth, Boston Red Sox
Omitting the comma between proper names causes them to be treated as one single long name, so a search for Babe Ruth Boston Red Sox yields no results.
To find a phrase, use double quotation marks around it or hyphens between the words that are part of a phrase.
Use double quotation marks (" ") around words that must appear next to each other. For example, to find pages that describe stupid pet tricks, type: "stupid pet tricks" Without the double quotation marks, Infoseek finds sites that include the word stupid, sites that include the word pet, and sites that include the word tricks. The search results include information about "stupid Mac tricks," "stupid Internet tricks," and "stupid OS/2 tricks," as well as pages about funny animal antics.
Do not use single quotation marks (') in place of double quotation marks.
Use hyphens (-) between words that must appear within one word of each other. For example, to search for information about cable networks, type: cable-networks. Without the hyphen, Infoseek looks for sites that include the word cable and the word networks. The search results would include information about setting up ethernet and token ring computer networks. With the hyphen, Infoseek Guide finds references to radio or television cable networks such as CNN.
To find words that appear together, use brackets. InfoSeek finds words that appear within 100 words of each other, such as words you would expect to see in the same sentence or paragraph. For example, to find safety tips for using elevators, type: [elevator safety] Without the square brackets, Infoseek Guide finds sites containing safety information for different universities in the United States. With the brackets, it finds the home page for the National Association of Elevator Safety Associates.
To specify words that must appear in the results, put a plus sign (+) in front of them. For example, to
find city guides about San Francisco, type: city guide +San Francisco (Do not put a space between the plus sign (+) and the word.)
To specify words that should not appear in the results, put a minus sign (-) in front of them. For example, to find all resources that contain python but not monty, type: python -monty (Do not put a space between the minus sign (-) and the word.)

You can do your INFOSEEK search directly by typing in the keyword(s) in the space below and clicking on SEARCH.

Questions? For answers, send an e-mail to Dr. Write.

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