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Boolean Basics for Search Engines
The Reference
Department has a website that provides a wealth of information
to researchers, students and net surfers. Check us out at:
http://www.liu.edu/cwis/cwp/library/ref/refhome.htm
Click on the Virtual
Reference Collection for links to many Search Engines that will
help you find information by name or subject on the Web. But rummaging
through the Web can take forever, unless you know how to refine your search
by using special commands. Below are explanations of some of these commands.
Some search engines alter these commands slightly, so click on their help
buttons for instructions first.
BOOLEAN LOGIC was developed by a 19th century English mathematician,
George Boole. It allows you to combine topics to make your search more
specific or broader. The most common Boolean operators are AND,
OR,
NEAR,
and NOT.
AND (e.g., teenage AND pregnancy) will look for only those sites
containing BOTH topics, and creates a narrower and more specific search
than OR.
OR (e.g., teenage OR pregnancy) will look for all sites containing
EITHER teenage or pregnancy, but not necessarily both. Therefore it is
a much broader search. You would more likely use OR to include various
terms for a given topic. For example, teenage OR adolescent will cover
sites that use either term for that age group.
NEAR (e.g., teenage NEAR pregnancy) will find those keywords
in proximity to each other. (Check the Help screens for each search engine
to determine usage.)
NOT (e.g., pregnancy NOT abortion) will look for all sites relating
to pregnancy but exclude all that mention Click abortion.
QUOTATION MARKS can be used in some search engines such as AltaVista
to retrieve a particular phrase such as "teenage pregnancy" or "Long Island
University". Other search engines will simply treat the words as separate
terms, and look for sites that include any of the terms or all of them.
WILDCARDS are a form of truncation. By inserting an asterisk
(*), called a "wildcard," after or in the middle of a word you will retrieve
plurals, suffixes, and alternate spellings. For example, cultur* will retrieve
culture, cultures, or cultural. Wom*n will find woman or women.
PLUS AND MINUS SIGNS are similar to AND and NOT. A plus sign
(+) placed before a term will retrieve only documents containing that term.
A minus sign (-) placed before a term will exclude it from the search:
e.g., teenage + pregnancy -abortion
NESTED SEARCHES are groupings within parentheses that incorporate
more terms into a search request, and can make your search more precise
or more thorough. For example: (teenage or adolescent) AND (pregnancy or
Planned Parenthood) AND smoking. While some search engines allow you to
form such complicated search requests, combining different Boolean operators
should be done carefully.
Search Engine Strategies
The easiest way to search the World Wide Web is to use a search engine
which is a sort of Internet gateway. Also called "spiders" or "crawlers",
they locate websites on the Internet, catalog them, and create links to
them. These engines scan millions of sites on the Web for keywords, phrases,
subjects, titles, and names. There are more than 260 search engines already
trolling the Web, and that number continues to grow. Below are a few of
the most popular ones, and some tips on searching them. Additional ones
are listed under Search Engines on the
Virtual Reference Collection page.
ALTAVISTA (www.altavista.digital.com)
Fast and comprehensive, AltaVista (begun in 1995) is one of the largest
search engines in terms of pages indexed. It covers the entire Web and
Usenet (a collection of user groups within the Net). With over 30 million
sites indexed, this search engine often retrieves an abundance of hits,
but advanced searches are easily accomplished, and it supports phrase searching.
It also prompts you to refine searches by requiring or excluding topics.
EXCITE (www.excite.com)
Launched in 1995, it offers the best of both worlds: powerful search
engine and well-organized index. Excite helps you refine or expand your
search by offering suggested terms and asking if you wish more documents
like the ones it found. It also has a list of reviewed sites, a Newstracker
to help you follow your personal news interests, a chat room, and a City.net
feature, with guides to more than 4,000 destinations around the world.
Since Excite indexes over 50 million sites, you may get more hits than
you want unless you narrow your search.
HOTBOT (www.hotbot.com)
One of the most comprehensive search engines, Hotbot was launched in
1996 by Wired Magazine. It uses pull-down windows for Boolean options and
for date, location, and other refinements. You can also specify media,
selecting pages with sound, still and video. Covering over 54 million sites,
Hotbot has useful search aids and advanced search features. Like Excite,
Lycos, AltaVista and Yahoo, it offers free email accounts.
LYCOS (www.lycos.com)
Lycos (Latin for "wolf spider") is one of the oldest search engines,
running since 1994. The 66 million sites indexed can be searched for text,
pictures, or audio, with results viewed in a choice of formats. It also
has preselected subject categories. Clear help pages guide you through
simple and customized searches. Lycos also offers a number of features,
such as City Guide, Companies Online, News Headlines, and its selection
of the top 5% of the most popular websites. Its own gallery of 80,000 pictures,
with access to 18 million web images makes this a good site for retrieving
graphics. Perhaps because of its size, Lycos tends to be slow to access
and retrieve search results, but its versatility is impressive.
INFOSEEK (www.infoseek.com)
One of the smaller engines, it searches 500,00 web pages but provides
accurate and relevant hits and designates Select Sites with a mark. Under
Search Tips you can find simple ways to achieve optimum results. Use capitals
for proper nouns. The Extra Search Precision feature (E.S.P.) will give
better results with one or two word searches. As in AltaVista, phrase searching
is available using quotation marks. Preselected categories on the main
screen allow you to narrow your search. [Note: this site has been taken over by
go.com]
GOOGLE! (www.google.com)
This new kid on the block improves the relevancy of your search results
by considering the links to a site, and it also gives you excerpts of the
matching text.
NORTHERN LIGHT (www.nlsearch.com)
Besides indexing web pages, it also classifies documents by topic.
Also "Special Collection" documents from materials not generally available
on the Web can be searched for a fee. You can use boolean operators, parenthetical
expressions, phrase searching, and truncation symbols: Use * for multiple
characters and % for only one.
Directories
Directories are created and organized by humans, and sites must
be submitted and then categorized. Sometimes you can achieve better results
using directories over search engines. One of the oldest and most popular
website directories is Yahoo!
YAHOO! (www.yahoo.com)
More a directory than a true search engine, Yahoo! may be the easiest
place to begin your search because of the preselected subject categories.
Additional features include: Maps, People Search, a telephone and e-mail
directory, and the latest news, sports, and stock quotes. Weekly Picks
offers the latest additions to the Yahoo index of 370,000 sites. If Yahoo
can't find anything in its own database, it will automatically direct you
to its mammoth search engine partner, Inktomi which indexes 110 million
Web pages.
MINING COMPANY (www.miningco.com)
This directory holds a network of sites selected and indexed by subject
specialists or "Guides". Each "GuideSite" treats a single topic with feature
articles, links, discussions, and site reviews. [Note: this site has been taken over by
about.com]
Metasearch Engines
Unlike true search engines, metacrawlers don't search the web themselves;
they compile results from other search engines and present them to you.
The following are some examples. You might want to try one of these first
to see which search engines will find the best information on your topic.
DOGPILE (www.dogpile.com)
This metacrawler covers 13 Web search engines, more than two dozen
on-line news services or other types of sources, and sorts the results
by the search engine that found them. It's a good starting point to see
which one will retrieve the most.
METACRAWLER (www.metacrawler.com)
This metasearch site compiles the results from Yahoo, Excite and five
other search engines. It is a good way to get a quick view of what's out
there, but it is difficult to refine searches.
SEARCH ENGINE WATCH
(www.searchenginewatch.com)
Try this site for the latest information on many search engines and
directories.
Final Tips
Most search engines provide some basic and advanced
search tips. Some let you refine your search as you go along, by prompting
you with suggested terms, or by allowing you to add your own. Always check
each search engine's Help screens for specific instructions for
that system.
Remember that search engines vary in their coverage, their features,
and their mechanisms for choosing the most relevant sites for your topic.
Try several to get the best results. Also keep in mind that search engines
are always changing, and new ones are being added. Experiment to find the
ones that work best for you.
For more information or further instruction in the use of these
search engines or other web-based resources, come to the Reference Department.
Jackie Elsas, elsas@liu.edu
Mara Rosenthal, mrosenth@liu.edu
Updated 07/01 by MKBB
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