Search sites provide anyone
on the web with the apparently magical ability to search large
areas of the Internet in seconds.
The first popular Internet search engine was the Wide Area
Information Servers (WAIS),
developed by Brewster
Kahle for Thinking Machines Corporation in 1988. A nice
flow chart of the relationship between different search engines
from 2001 has been drafted by bruceclay.com.
Search engines enable you to search the Internet for information
you're interested in, such as "home
AND garden AND tomatoes" or "exercise
AND arthritis". Different engines combine criteria
such as those listed below in various scoring algorithms to
determine which sites to return first in response to each query:
- Number of other sites that link to the site.
- The search words are in the Meta tag.
- The search words are in the URL.
- The search words are in the Title.
- The search words are near the top of the page.
- The search words are in the Keyword tag.
- There are repeated occurrences of the search words.
Search engines don't have time to search the whole web every
time you make a query, so they first build up a large database
with automatic computer programs called robots that
continuously browse the web, twenty-four hours a day, to find
new sites and old sites that have been updated. The robots
read the text on each page and add it to the search engine's
database. Some search engines record just displayed text, while
others index picture tags, link names, and all other textual
Mathematically, the data structures that these sites use for
storage of their databases are special types of "trees" that
are particularly compact and can be searched very quickly.
The cost of storage and access time for these trees is usually
related to the number of consecutive characters indexed, so
most search engines limit the length of any given search word
to a defined number of characters, such as 32, although the
whole query can usually be much longer.
Resources. The following resources provide more information
about search engines.
- The searching section
provides tips and techniques to help get the best possible
results from search engines in the minimum possible time.