What is a search engine?
A search engine
is an information retrieval system designed to help find information
stored on a computer system. What is a Web search engine?A Web search engine is specific to the
World Wide Web. Information may consist of web pages, images, or other
types of files. Some search engines also mine data from newsbooks,
databases, or open directories. Unlike Web directories, which are
managed by human editors, search engines do not need human intervention.
Humans program algorithms that retrieve results. Sometimes, search
engines are a mix of direct human intervention and algorithms.
Examples of Search Engines
Google: www.google.com Yahoo!
Search: www.yahoo.com Ask.com: www.ask.com Exalead: www.exalead.com/search Gigablast: www.gigablast.com What do they have in common?
- The default Boolean
operator AND - if you type in two or more words, you don't need to use
AND as a Boolean operator in any of these search engines.
example: acid rain is treated as acid AND rain without the Boolean
- The Boolean operator OR, if you enter it in
capital letters so the system doesn't think this is just a word.
NOTE: If you use a Boolean
operator in any of these search engines, BE SURE TO USE ALL CAPITAL
What about differences?
- The capability of excluding words, but you
can't always just use NOT.
- In Google, Yahoo, and
Ask.com, you must use a hyphen and there must be no space betwen the
hyphen and the word you wish to exclude;
- example for
Google, Yahoo, and Ask.com: acid -rain
- in Exalead and
Gigablast you can use NOT, AND NOT, or a hyphen. This is useful if you
are looking for information about acid from a chemistry perspective, for
example, and don't want acid rain for this particular search
- examples for Exalead and Gigablast:
- acid NOT
- acid AND NOT rain
- acid -rain
- Adjacency: if you enter a phrase in quotation marks, e.g. "acid
rain," you will retrieve only those results where acid and rain are next
to each other. The system searches for the following string of
characters: a c i d blank r a i n
- Nesting: to tell the system in what order to
execute your search string. There are several ways to do that.
- One is to use quotation marks around the parts you want to
appear together and enter them with another term you want
Example: "acid rain" chemistry
- Another is to use
parentheses around the part you want searched first
Example: (acid rain) chemistry (NOTE: in this case, the system is
searching acid AND rain first and then combining the results with a
search for chemistry, so you will get more results than in the previous
- Stop words: these ignore common words,
such as the, a, etc.
- Example: Jump the shark will
search jump shark
- Include common words: you can use
quotations for this or put plus signs between the words (no spaces)
- Example: jump+the+shark; "jump the shark"
- Size: the number
of web sites that are searched
- Google: probably the
largest, although in 2007, Yahoo! Search did an upgrade and claimed to
be the largest. In our assignment posted January 7, one of our students
found that out, as I saw on the student's blog.
Search: approx. 22 billion
- Ask.com: over 2 billion
Exalead: over 8 billion
- Gigablast: over 12 billion
- Default rankings: how the web sites are ordered when they
show up on your screen
- Google: by popularity
Yahoo! Search, Exalead, Gigablast: by relevancy
- Ask.com: by
- Modifying default
rankings: there are ways to change how the search engine lists the
- Google: view:timeline; view:info, view:map
Exalead: click "only recent results" at top of search results; date
sorts in "Advanced Search" by oldest or newest, or you can use sort:old
- Gigablast: Pipe between terms ranks by the term
after the pipe, e.g. acid|rain will rank by the word rain
Yahoo! Search, Ask.com: no modification
suggestions: search engines will try to give you "hints" of various
- Google: sometimes gives search suggestions in
results, e.g., for mis-spellings
- Yahoo! Search: suggests
related searches if other Yahoo searchers have searched the same topic
- Ask.com: suggests narrower or broader search terms
Exalead: offers Narrow your search to focus the search in many ways
Gigablast: provides Giga Bits at the tops of the results to reflect
the main themes in the results
There are other tips
and tricks you can apply to search engines, but you have to know which
tip or trick applies to which search engine. The ones I've provided
above are probably the most common ones you will need.