Transcript Web Design/Internet Essentials

Web Design/Internet
Essentials
Search Engines and
Searching the Web
Search Engines
• Search Engine Basics
• Formulating Searches
The Web and E-mail
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Search Engine Basics
• A Web search
engine is a
program
designed to
help locate
information on
the Web by
formulating
simple keyword
queries.
Search Engines
• A search engine is helpful in locating information
for which you may not know the exact web
address on
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web pages on various topics
locating specific web pages
images
videos
• There are thousands of search engines
available.
Search Engines & Types
Google
Lycos
Alta Vista
Yahoo
WebCrawler
Excite
MSN
AOL
HotBot
Search engine
Directory
Search engine
Directory
Search engine
Search engine
Directory
Directory
Search engine
The Different Types of Search
Engines
• Although the term "search engine" is often
used indiscriminately to describe:
– Web crawler search engines
– human-powered directories
– everything in between
• they are not all the same.
• Each type of "search engine" gathers and
ranks listings in radically different ways.
How do search engines work
• Contains four parts
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a web crawler
an indexing utility
a database
a query processor
• Web crawler: combs the
web to gather data
• Indexing: processes the
information gather by the
crawler
• then stores key terms and
URL’s in a database
• Query processor: allows
you to access the
database by entering
keyword
Web Crawler
• Crawler-based search engines such as
Google, compile their listings
automatically
• They "crawl" or "spider" the web, and
people search through their listings
• Spiders scour the web on a regular basis.
• Listings are what make up the search
engine's index or catalog
• The index can be defined as a massive
electronic filing cabinet containing copies
of every web page the spider finds
Directories
• Directories depend on human editors to
compile their listings
– Webmasters submit an address, title, and a
brief description of their site, and the
submission is reviewed
• After a web site makes it into a directory it
is generally very difficult to change its
search engine ranking
Hybrid search engines
• Some search engines offer both crawlerbased results and human compiled listings
called “hybrid search engines”.
• They typically favor one type of listing.
• Yahoo usually displays human-powered
listings.
– It also draws secondary results from Google
– which may display crawler-based results for
more ambiguous queries
Search Engine Basics
• Search engines require you to enter a
word or phase, “search text” or “keyword”
that describe the item you want to find
• They often respond with results that
include thousands of results, whose
content varies based on the information
you are seeking.
Formulating Searches
• Most search engines are not case sensitive
(Shift key usage not necessary)
• Search engines ignore common words like:
(and, a, & the) there is no need for them.
• To search for an exact phrase, enter it in quotation marks.
•
When you enter multiple terms the query processor
assumes you want to see web pages that contain all of
your terms.
• The asterisk (*) is referred to as the wildcard charter.
Boolean Search
• A Boolean operator is a word or symbol that
describes a relationship between keywords,
– Helps you create a more focused query
Ex.1 poverty and crime Ex.2 poverty and crime and gender
Ex.3 cats not dogs
Ex.4 cats or felines
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Boolean Logic
Example 1: +dyslexia
+adults
Example 2: radiation
-nuclear
Key word Search
Most search engines work with keyword queries in which
you enter one or more words
Ex. Mountain Bike
Search results
Open your browser and go to the
website below and watch:
The Animated Internet: How
Search Engines Work
http://www.learnthenet.com/ENGLI
SH/animate/search.html