Transcript Searching the World Wide Web

Searching
the World
Wide Web
CMP 101
Introduction to
Information Systems
L02. Internet Search
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What is the World Wide Web?
Billions of Documents
– Accessible via the Internet
– Viewed by a web browser.
Web documents contain hyperlinks
– Allow readers to jump from one web
document to another
– Gateways to audio and video broadcasts,
animations, and more.
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What is a Search Engine?
A collection of software
– Locates words on web pages
– Ranks and indexes the words
– Creates a database that you can
search.
When using a search engine, you
search the database that has been
created (not the Web).
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How Does a Search Engine Work?
Robots, Spiders, Crawlers – Oh My!
– visits web pages
– collects words and hyperlinks
– gives words to the search engine for
ranking and indexing
– differing strategies for crawling yield
different results
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How Does a Search Engine Work?
Ranking and Indexing
– Meta-information
• the number of times a word appears on a page
• the word’s location on a page
• other much more sophisticated information.
– differing strategies yield different results
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Subject Directories
Categorical listing of topics with
links to individual web sites.
Created with the help of human
editors
Editors rate and rank the sites
Good for narrowing down a topic or
browsing a large list of topics.
Examples include: Yahoo! Directory (dir.yahoo.com), and
Gigablast (gigablast.com).
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Individual Search Engines
Create and maintain a database of
indexed and ranked words for
searching.
Good to use if looking for specific
information about a topic.
Examples Include: Google (google.com), Yahoo! Search
(yahoo.com), and Ask (ask.com).
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Metasearchers
Searches multiple individual search
engines
Presents results in one convenient
list.
Good to use to get a feel for how
much information is available on a
topic.
Examples include Dogpile (dogpile.com), Mamma
(mamma.com), and Clusty (clusty.com).
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Search strategy kickoff
Determine your needs:
What are you
looking for?
Type of search
Broad range of topics
in a specific category
Subject
Directory
A lot of information
about a specific topic.
Meta-search
engine
Specific facts
Examples
 Astronomy
 Football
 Aurora Borealis (Northern
Lights)
 Indianapolis Colts
 Aurora Borealis particle
speed
Individual
Search Engine  Peyton Manning’s passing
statistics
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Basic Search Techniques
Be specific
Put words in the order you would
normally expect them to appear.
Avoid using common words.
Consider synonyms.
Use search focus options: (i.e.
images, videos, or blogs).
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Advanced Search Techniques
Boolean logic (AND, OR, NOT):
– Boolean AND
• Include all words.
• Narrows your search.
– Boolean OR
• Include any of the words
• Broadens your search.
• Useful for synonyms.
– Boolean NOT or AND NOT
• Excludes words
• Narrows your search
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Advanced Search Techniques
Implied Boolean operators (+, -)
– Used in place of the Boolean AND and
Boolean NOT.
Phrase searching (“ “)
– Place quotes around a phrase.
– Returns documents where the words
appear as a phrase (side by side).
Wildcards (*):
– Used for plurals, alternative endings, or
alternative spellings,
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Advanced Search Techniques
Advanced search form
– With all the words: Same as using
the AND or plus (+) operator.
– With at least one of the words:
Same as using the OR operator.
– With the exact phrase: Same as
using quotes.
– Without the words: Same as using
the NOT or minus (-) operator.
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Analyzing results
Scan through the first five to ten
pages of results.
Consider synonyms.
Use the NOT or minus (-)
operator.
Broaden your search.
Narrow your search.
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Odds and Ends
Search engines ignore some pages.
– dynamic (created on demand) such as
a request for account information,
– require registration or a login (like the
Wor-Wic research databases).
database not always up-to-date.
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Odds and Ends
Search within a site.
Search for individual words or
phrases on a page
– Edit > Find on this page… on the
menu
– Search List arrow,
Find on this Page….
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