4. Introduction
With the arrival of the WWW came
the widespread availability of online
information
Answers to your questions are
somewhere on the web, but how do
you locate them?
5. DIRECTORIES
• Method of finding and organizing
web information
• Offers a hierarchical representation
of hyperlinks to web pages and
presentations broken down to topics
and subtopics
• Review and classified by human
editors
6. Directories : classification
General Specialized
•Also called web
directory or subject
directory
•Top level provides a
wide range of broad
topics. E.g. Music /
Entertainment.
•Also called subject
guides or gateway pages
•Deals with a variety of
topics. E.g. law,
medicine.
Benefits
Easy to use
Need not know what you are looking for
7. Search Engines : introduction
• A computer program
• Submit a query describing the
information you want to locate
• Searches its databases to try and
match your query
• Collates and returns a list of URL’s
which matches your query
• Permits you to revise and resubmit a
query
8. Search engines : classification
General Specialized
•Also called vertical
search engine or a topic
search engine
•Retrieves information
from a database that
contains information on a
wide variety of topics
•Provides in-depth
information on specific
topics that may be
valuable
•Exists for a multitude of
topics
•MP3s
•Shopping
•News etc
Not as easy to use as directories.
WHY??
9. Metasearch Engines
• Does not have their own database of
information
• Calls many search engines to do the
actual work
Advantage:
You can access a number of
different search engines with
a single query
Disadvantage:
You will get a lot of results
which will not be of interest
to you. Therefore you will
spend a lot of time evaluating
the results and deciding
which link to follow
11. Boolean Queries : AND
operator
A
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
B
B
12. Boolean Queries : OR operator
A
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
B
B
13. Search Strategies
• Determine which search engine
• Possesses a user-friendly interface
• Has a easy-to-understand, comprehensive
documentation
• Is convenient to access; that is you do not
have to wait several minutes before being
able to submit a query
• Contains a large database
• Does a good job in assigning relevancy
scores
