Transcript PowerPoint Presentation - Searching for Information

Browsing and the Use of Search
Engines on the WWW
Search Engines categorize the World
Wide Web’s many pages
The Internet and the WWW--What’s the Difference?
The Internet is the global association of
computers that carries data and makes the
exchange of information possible. The World
Wide Web is a subset of the Net--a collection
of interlinked documents that work together
using a specific Internet protocol called
HTTP. In other words, the Net exists
independently of the Web, but the Web can't
exist without the Net.
http://coverage.cnet.com/Content/Features/Techno/Networks/ss03.html
World Wide Web - WWW
World Wide Web is a series of connected (linked)
documents and computers that are a subset of the
Internet (remember definition??)
• Web pages/documents
– are written in HTML
– Hypertext Markup Language
is text plus codes/tags to tell
browser how to display
elements in the web document
– contain links to other HTML
documents
– are linked by http:
hypertext transport protocol
– contain hypermedia
links to:
• graphical images
• sound clips (audio)
• video files (motion)
• Web site - collection of
linked Web pages with
common focus or theme
• Home pages – main
page of Web site
Web Browsing
• requires a text-based or graphical browser
– text-based browser - Lynx
– graphical (GUI) browser - Mosaic, Netscape Navigator
(Netscape), Internet Explorer (IE)
• uses “addresses” of links to browse
• WWW link “address” = URL
– uniform resource locator
– may use http, ftp, telnet, or another protocol
• WWW address format:
http://www.sunyocc.edu/~bryantm/index.html
(protocol + domain name + folder or directory pathname + file name)
Search Engines:
What They Are and How They Help Us Find
Information
• Search engines are special programs to make
browsing more efficient, organized, and focused
• Also known as tools or utilities
• They use automated programs called spiders/robots to
find and organize indices of information from
Internet/WWW into databases
• They offer various methods for searching using
subject directories, keywords, phrases, concepts
Search Engines:
A Few Examples
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Yahoo
Lycos
Alta Vista
Discover
Infoseek
Excite
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Metafind
Metacrawler
WebCrawler
Ask Jeeves
Google
Dogpile
Mamma
Search Engines:
How to Use Them
• Simplest is to use Search or Net Search through
browser such as Netscape or Internet Explorer
• But going directly to engine page by using it’s URL
may be more effective to begin
– e.g.,
use Ask Jeeves by going to:
www.askjeeves.com
• Type keyword(s) or phrases in the search box
• Obtain ranked “hits” or matches
• Click on links to use these hits
• And . . . . away you go!
Search Engines
• Robots called spiders collect information
from web servers all over the world.
• What is collected and how it is organized
marks the differences in search engines.
Search Engines
Subject Directories
• Subject Directories use a combination spiders and
human beings. The spiders collect data about Web
Sites and the information is used by people who
organize them into topics.
• They can be referred to as "trees" because they start
with a few main topics and branch into subtopics.
• Some include a search option which will let you search
all documents or just one branch of the tree.
Search Engines
Subject Directories
• Because humans organize the websites in subject
directories, they can be time savers if you know the
topic you are looking for.
• Directories are also useful for finding information on a
topic when you don't have a precise idea of what you
need
• http://www.yahoo.com/
Search Engines
Key Word Searches
• This is the most common form of text search on the
Web.
• Most search engines do their text query and retrieval
using key words.
• The author of the Web page identifies the keywords.
• The search engine can also identify what it believes to
be keywords. Words that are mentioned toward the
top of a page and words that are repeated throughout
the document are more likely to be deemed key.
Search Engines
Key Word Searches
• Some sites index every word on every page.
Others index only part of the document
• Full-text indexing systems generally pick up every
word in the text except commonly occurring stop
words such as "a," "an," "the," "is," "and," "or,"
and "www."
• Some of the search engines discriminate upper
case from lower case; others store all words
without reference to capitalization.
Search Engines
Key Word Searches
• Lycos indexes the title, headings,
subheadings and the hyperlinks to other
sites, along with the first 20 lines of text.
• AltaVista claims to index all words, even
the articles, "a," "an," and "the."
Search Engines
Key Word Searches
Drawbacks:
• Trouble distinguishing between words that are
spelled the same, with different meanings (i.e.
score: 1-cut or scratch a surface; 2-record of points, used
in sports; 3- paper copy of music).
• Trouble with stemming, other tenses of a keyword
(i.e. do, doing, done)
• Cannot return hits on synonyms of keywords (i.e.
huge, enormous … )
Search Engines
Concept Searching
• Unlike keyword search systems that only look at
what words are used, concept-based search
systems look at how the keywords are used to try
to determine what you mean, not just what you
say.
• This is also known as clustering -- which
essentially means that words are examined in
relation to other words found nearby.
Search Engines
Concept Searching
• There are predefined concepts. The search engine
keeps lists of word groupings that mean something
(i.e. “home run” = baseball)
• When these groups of words or phrases appear
close to each other in a page, the search engine
concludes, by statistical analysis, that the piece is
"about" that particular concept even if the word
for the concept doesn’t appear in the page.
Search Engines
Concept Searching
Examples:
• http://www.lycos.com.
• http://www.alltheweb.com All The Web (FAST)
• http://www.google.com
Concept-based indexing is a good idea, but it's far from
perfect. The results are best when you enter many words
which roughly refer to the concept you're seeking
information about.
Search Engines
Metasearches
• Meta-search engines (also know as multi-threaded
engines) search (use) several major engines at
once.
• They are search engines that invoke other search
engines.
• They act as a middle agent, passing your search
string to other major search engines and then
return the initial results from each of them.
Search Engines
Metasearches
• Meta-search engines do not crawl the Web or
maintain a database of web pages.
• Because the major search engines often produce
very different results, meta-search engines provide
a quick way to determine which engine provides
the best match for your search string.
• Because search engines vary in ability to interpret
complex searches, meta-search engines work best
with simple searches.
Search Engines
Metasearches
Examples:
• ixquick http://www.ixquick.com/ ranks results
based on the number of "top 10" rankings a site
receives from the various search engines.
• qbSearch http://www.qbsearch.com Lets you
choose which search engines to use.
• Kartoo http://www.kartoo.com shows the results
graphically with sites interconnected by keywords.
• Dogpile http://www.dogpile.com displays results
from each search engine individually.
Specialty Search Engines
News Search Engines
• A way to search for the latest news stories from
hundreds of sources on the web.
• These services provide exceptionally good results
for current event searching, because they crawl
only news sites and revisit these sites several times
per day.
– AltaVista News http://news.altavista.com/
– Yahoo News http://news.yahoo.com/
– Moreover http://www.moreover.com/news/
Specialty Search Engines
Multimedia Searches
• Multimedia search engines will help you locate
sound, image or video files.
– Fast Multimedia http://multimedia.alltheweb.com/
let’s you specify the media type including: JPEG, GIF,
BMP, MIDI, MP3, Wave, AVI, MPEG & QuickTime.
– Google Images http://images.google.com a very large
graphics collection
– SpeachBot http://speechbot.research.compaq.com/ lets
you search for streamed audio & video, media is hosted
and played from other websites
Specialty Search Engines
Newsgroup Searches
• Newsgroup search engines help find a relevant
newsgroup for a particular topic
• They provide a way to pinpoint discussions about
specific interests online
– Google Groups http://groups.google.com/ search
through the most complete list of newsgroup postings.
Formerly Deja News, the service was acquired by
Google in early 2001.
Specialty Search Engines
Financial Search Engines
• Provides quotes, financial data, related web sites
and much more when you enter the name of a
company or a stock symbol
– DailyStocks.com
– TradingDay.com
– justQuotes.com
Specialty Search Engines
Expert / Answer Searches
• Expert Search Engines specialize in providing answers.
• They emphasize providing factual information rather than a list of
Web sites.
– AllExperts.com http://www.allexperts.com Pick a category, then choose a
volunteer, then ask your question.
– Ask Jeeves http://www.askjeeves.com/ Ask Jeeves has editors who try to
find sites that answer popular questions. These answers are listed in the
"Click Ask below for your answers" section at the top of the search results
page at Ask Jeeves.
– Information Please http://www.infoplease.com/ Information Please
almanacs are favorites among researchers who need trustworthy facts. This
site allows searching across Information Please's various almanacs, its
encyclopedia and its dictionary.
Specialty Search Engines
People / Person Searches
• Person Search Engines aid in locating people
• You can find e-mail addresses, mobile phone directories and
white page directories at http://www.bigfoot.com/
• http://www.whowhere.lycos.com lets you look up e-mail
addresses, residential listings, and toll-free 800 numbers
• http://www.switchboard.com is a white pages service that
enables you to find people and businesses.
• At http://people.yahoo.com , you can search to find a person’s
e-mail address or street address. You can also search thousands
of public databases to find property records, licenses, and court
records
Specialty Search Engines
Government Searches
• The search engines below allow you to search for
official government information.
– http://www.firstgov.gov/ the official US gov. portal
– http://www.searchgov.com/ is a search engine that
crawls all us government web sites
– http://www.usgovsearch.com/
– searches across US government web sites and
information from the NTIS (National Technical
Information Service).
Specialty Search Engines
Maps and Direction Searches
• There are sites that allow you to get maps
and directions based on gps data
– http://mapquest.com enables you to find over
three million locations worldwide, print driving
directions, and create and save personalized
maps.
– http://maps.yahoo.com/ also allows you to
create custom maps and driving directions
Search Engines
• Search engine technology has not yet reached the
point where humans and computers understand
each other so there will continue to be changes in
search engines.
• A good place to learn about search engines is the
Search Engine Watch, where you will find
announcements of the latest search services and
Web searching tips. Hosted by Internet.com, you
will find the Search Engine Watch at
http://searchenginewatch.internet.com
• .
Search Strings
Advanced Search Syntax
• To most effectively use search engines, use
advanced search tools and syntax
• Many search engines have an ‘advanced
search’ link that provides a form for
accessing advanced search term structure
• Using boolean logical operators (AND, OR,
NOT) can narrow the scope of your search.
Search Strings
Advanced Search Syntax
• BOOLEAN AND returns Web pages in which
ALL search terms are present
• The search engine will not return pages that
contain only one of the words, it will only return
pages where ALL the words appear somewhere on
the page. (e.g. poverty AND crime)
• AND helps to narrow your search results by
limiting number of resulting pages
Search Strings
Advanced Search Syntax
• BOOLEAN OR will retrieve Web pages where AT
LEAST ONE of the search terms is found
• The search engine to retrieve web pages
containing ANY and ALL keywords. (e.g.
college OR University OR campus)
• OR can increase your search results
Search Strings
Advanced Search Syntax
• BOOLEAN AND NOT logic excludes records from your
search results.
• NOT tells the search engine not to retrieve any web pages
containing the identified term. (e.g., cats NOT dogs, “calico
cats” NOT cloth
• Be careful when you use NOT. Make sure the term you do
not want doesn’t limit any pages you are looking for.
– For example, there may be a page on pets that has a section on cats
and a section on dogs. The above search would not retrieve it and
a useful page could be missed.
Search Strings
Advanced Search Syntax
• In some search engines, the plus sign (+) is the
equivalent of AND, and the minus sign (-) is the
equivalent of NOT
• There should be no space between the plus or
minus sign and the keyword. (e.g. +diamond –ring)
• Some search engines provide a ‘search the results’
option, this is an implied AND of the search terms
• NOTE: AltaVista's Simple Search requires the use of plus
and minus rather than AND, OR, and AND NOT.
Search Strings
Advanced Search Syntax
• PHRASE SEARCHING
• Surrounding a group of words with double quotes
tells the search engine to only retrieve documents
in which those words appear in that exact way.
(e.g. "global warming“)
• Phrase searching is a powerful search technique
for significantly narrowing your search results.
Search Strings
Advanced Search Syntax
• You can combine advanced search syntax to
provide even more accurate results
– e.g. You can use phrase searching with Boolean logic.
+"heart disease" +cause
"heart disease" and cause
The above example tells the search engine to retrieve
pages where the words heart disease appear side-byside and the word cause appears somewhere else on the
page.
Search Strings
Advanced Search Syntax
• Field searching is an effective technique for Web
searching and narrowing results
• A Web page has many components, some of which
are searchable: title, domain, host, URL, and link.
• To search for a term only in a specific area of a Web
page, use the section name followed by a colon
directly before the search word (e.g. TITLE:Arizona)
• There is no space between the colon (:) and the
keyword.
Search Strings
Advanced Search Syntax
• The TITLE element of a Web page is used to identify
the content and every page should have one TITLE.
– A TITLE SEARCH instructs the search engine to only return
web pages where the search phrase appears in the TITLE
(e.g. title:realtor)
• The LINK SEARCH will search only in websites that
are linked to the site you list (e.g. link:www.sunyocc.edu)
– you can use this to identify any links to your page
– Researchers use link searches for conducting backward
citations.
Search Strings
Advanced Search Syntax
• A DOMAIN SEARCH allows you to limit results
to pages from high level domains (domain:.edu)
• The URL SEARCH limits search results to web
pages where the keyword appears in the URL or
website address. (e.g. url:recipes)
– The URL search may not work with all search engines.
Google will mistake it for an exact phrase.
Search Strings
Advanced Search Syntax
• With the HOST SEARCH, you can search all
the pages at a website (recorded by the
search engine) for keywords or phrases of
interest.
• e.g., host:www.disney.com
• This can be useful when you need to find
something located at a large site that does
not have an internal search engine.
How to Use What We Find
• We do need to be responsible and
informed about ethical and
copyright issues when using
Internet/WWW resources
• Find and just read for reference
• Save/download to disk or diskette
– Files - choose File, Save As, filename
– Images - right-click on image to save
copy to disk on PC or control+click on
Mac
• Print out
– use Print Preview to select pages to
print
– print selection by highlighting desired
text
– use Copy and Paste to put text into a
new word processing document
How Do We Find Info on the
WWW?
•Use various search engines for what
they do best
• Use good, well put-together search
strings