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Boolean Searching
Boolean searching (the name comes from "Boolean
algebra") involves the use of words called
operators to connect your
search words. The most commonly used operators
are the words AND, OR,
and NOT. Boolean searching is
used in most library catalogs, including Quest,
as well as most electronic periodical indexes.
AND placed between two words
requires that both the first word and the second
word occur in your search results. For example,
in this Quest search,
alcohol
and memory
items retrieved by Quest would have both the
words "alcohol" and "memory" somewhere in the
titles, subject headings, or other fields. If
only one of the words occurs in a record, it
won't be retrieved by the software. The
AND operator allows you to narrow a
search by requiring that more than one word or
concept be present in the resulting items.
OR
placed between two words requires that
either one word or the
other word must occur in the resulting items.
If an item's description includes both words,
that also qualifies as a match.
woman or
women
In this example, Quest would give you a list of
books, etc., that contained either the word
"woman" or the word "women." As you can see,
using the OR operator allows
you to look for synonyms or related terms in one
search, rather than requiring you to perform
multiple searches for each related term.
NOT
placed between two words requires that
the first word be found without any occurrence
of the second term. In this example,
mexico
not new
Quest would retrieve all the records containing
the word "mexico," but then it would throw out
all those using the term "new." This would be
one method of finding materials on Mexico but
avoiding those about "New Mexico." However,
you should be careful with this operator,
because you will sometimes exclude items you did
not plan to cut out. For example, the previous
search would have excluded a book with the
title, "New Perspectives on the History of
Mexico." Think carefully about what will be
excluded before you use this connector!
Combining
Operators
Boolean operators can be used more than once or
combined in a search statement. Parentheses
are often used to tell the online system the
order in which you'd like the operations
performed (just as you use them in math when
mixing addition and multiplication operators,
for instance).
(woman or
women) and religion
searches for either of the first words, then
requires that any records with one of those
terms must also have the word "religion;"
(behavior
or behaviour) and (rats or mice or rodents)
allows one to search for variant spellings of
the first concept and combine that with any one
in a series of related terms.
Because most library
catalogs and many periodical indexes have only a
small number of terms in their records, it is
usually wise to select no more than three or
four terms that must occur in a search result
(that is, terms that are connected by
AND). If your search ends up with no
results, you should re-try your search with
fewer required terms.
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Relevancy
Searching
Increasingly, electronic search software
provides some form of relevancy
searching or relevancy ranking. This
method of processing a search statement
is very common with web search engines
such as AltaVista and HotBot.
Relevancy
searching allows you to enter any number
of search terms to describe your topic.
The software then looks for the
occurrences of each of the terms you
entered (though sometimes ignoring less
important words like "the" and "of").
Any item which matches at least one of
the terms is retrieved. The results are
presented to you in a ranked manner
according to their perceived relevance
to your request.
Results
which are listed at the beginning of the
retrieval list are considered more
relevant than other items because these
types of conditions have been met:
-
all or
most of the search terms are present
-
the
search terms appear in the title or
abstract for the items
-
the
search terms appear in the first
paragraph or so of the documents'
text.
Because
relevancy searching will retrieve items
that match only some of the terms, and
these terms may occur in unimportant
places in the texts of the retrieved
items, this method will give results
when a Boolean search would not.
However, many of the results can appear
to be fairly irrelevant to the
searcher. Thus, if you know that you
are searching a database that uses
relevancy searching and ranking, it is
best to enter several terms rather than
just one or two; the more descriptive
you make your search, the fewer
irrelevant results you will retrieve. |
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