Search Engine Basics
- Search engines are tools that use computer programs called spiders
and robots to gather information automatically
on the Internet. With this information, they create a database.
- Each of the major search engines attempts to do the same thing-namely, index
a substantial portion of the Web-so they handle a huge amount of data.
- There are advantages to computer-generated databases. They are frequently
updated, give access to very large collections, and provide the most comprehensive
TIP: If you are looking for a specific
concept or phrase, a search engine is the best place to start. And you would
be smart to look in more than one, because each engine gives different results.
Some of the most popular search engines are in our annotated
list of selected search tools.
Search Engine Similarities
- All of the major search engines are similar in that you enter keywords,
phrases, or proper names in a search form.
After you click on search, submit, seek, or some other command button, the
database returns a collection of hyperlinks to your screen.
- The database usually lists them according to their relevance
to the keyword(s) you typed in, from most to least relevant. Search engines
determine relevance in different ways.
- All search engines have online help to acquaint you with their search options.
Two common search options that most search engines support are
Boolean searching and phrase
searching. Check out Using
the Web for Research for more details.
Common Search Features of Search Tools
Tip: Read the Help or Tips section to learn the options, features,
and idiosyncrasies of the search tool you're using.
Implied Boolean Operators
- and indicates that only those Web pages that have
both words in them will be retrieved
- or will result in Web pages that have either term
- not is used when a term needs to be excluded (in some search
engines, type and not)
- When ands and ors are used in one search statement, you must put parentheses
around the items that are to be performed separately.
For example, the nested expression
((rivers OR lakes) AND canoeing) NOT camping
will find resources that contain either the words rivers or lakes and the
term canoeing but not resources that contain the term camping.
This is called nested
- Shortcuts to and and not. If search engine supports this
feature, type "+" in front of a word that must appear, and "-" before a word
that must not appear. For example +myth +fire -job
- A string of words that must appear next to each other, for example, "global
- Retrieval of a root word and its different endings, for example, postmodern*
would retrieve postmodernist, postmodernism, and so forth.
- The capability limiting search results to parts of a Web page, for example.,
URLs, headings, summaries, and so forth. Supported by few search engines.
- Some search engines recognize capitalization in words and some don't. This
can be very important when looking for proper names, like Sting, or the Who.
Limiting by Date
- Some search engines allow you to search the Web for pages that were entered
between certain dates.
After determining whether your search has yielded too few Web pages
(low recall), there are several things to consider:
- Perhaps the search expression was too specific; go back and remove some
terms that are connected by Ands
- Perhaps there are more possible terms to use. Think of more synonyms to
OR together. Try truncating more words if possible.
- Check spelling and syntax (a forgotten quotation mark or a missing parentheses)
- Read the instructions on the help pages again.
If your search has given you too many results with many not on
the point of your topic (high recall, low precision), consider
- Narrow your search to specific fields, if possible.
- Use more specific terms; i.e., instead of sorting, use a specific type
of sorting algorithm.
- Add additional terms with AND or NOT.
- Remove some synonyms if possible.
For more details take a look at the Web pages
for Search Engines
Using Search Engines