The following table
outlines a variety of tools used to search for
information on the World Wide Web. It's a good idea
to become familiar with different directories,
search engines, metasearch engines, and specialized
tools because not a single one indexes the entire
Internet.
|
Directories
(also known as "virtual
libraries"
or "portals") |
Characteristics
-Index web pages
selected by editors
-Organized into
hierarchical subject categories
-Search a description
of Web pages, not the full-text
-May be annotated
|
Examples
|
|
Search Engines
|
Characteristics
-Use "spiders" or "knowbots"
(computer programs that roam the Web for
sites and keep the search engines up to
date) -Provide keyword searching of words in
pages or full-text of selected pages
-May not have subject
categories
-May not search
"invisible web"
of information stored in databases
|
Examples
To understand the
relationship between main search engines
click here
|
|
Metasearch Engines
|
Characteristics
-Search several
individual search engines simultaneously and
compile results -Only catch about 10 percent
of the search results of the engines visited
|
Examples
|
|
Specialized tools
|
Characteristics
-Provide a
subject-specific searchable database of
indexed web page content
-Capture content of
some of the "invisible web"
-Link to a list of
specialty search engines
-Link to a directory of
international search engines
|
Examples
|
Also note that
Crawler-based search engines, such as Google, create
their listings automatically. They "crawl" or
"spider" the web. Internet surfers get what search
engines gather, which means that the search is not
done in real time, hence resulting in some dead
links and changes in the URLs.
