Transcript power point presentation

search ENGINES
WHAT ARE SEARCH ENGINES?
 Huge
Databases of web page files that
have been assembled automatically by
machine.
 Two
Types:

Individual

Meta
BASIC COMPONENTS OF
SEARCH ENGINES
 SPIDER
(CRAWLER, LINK FINDER)
 INDEX
 SEARCH AND
RETRIEVAL MECHANISM
HOW DO SEARCH ENGINES
WORK
 Compile
their databases by employing
“spiders” or “robots” to scan through web
pages from link to link.
 Sites
 Once
with no links usually are missed
at a web site they index most of the
words on the available pages to the public.
IMPORTANT SEARCH
REMINDERS
 While
using search engines you are not
searching the whole web as it exist.
 You
are only searching the section which
is captured in a fixed index.
 Most
search engine indexes are not up to
date, but are working with news databases
that are.
PROS AND CONS

PROS


Provide access to
large portion of pages
on web
Best means for
searching web

CONS


the large number of
words indexed gives
back a lot of
responses with
nothing to do with your
search
You get long
documents that only
refer to your words
once
ARE ALL SEARCH
ENGINES THE SAME?
RANKING OF WEB PAGES
 Vary
from one search engine to another
 But all have the same objective to put best
sites at the top of the list

Look for location & frequency of keywords
and phrases

Check out title field

Popularity by number of links pointing to site
WHEN TO USE SEARCH
ENGINES
 BEST AT
FINDING UNIQUE:

Keywords

Phrases

Quotes

Info buried in full text of web pages