Slide 1:Search Engines
Slide 2:WWW
The “Public Web”
Currently estimated at over ______ pages
Private or “hidden” web: ____ that!
No search engine can search it all…
Google: covers less than ___ of public web
Slide 3:Search Engines
How do they work?
Software programs called “______” or “web ______”
Follow all links
Record info about pages they visit in enormous ________
Slide 4:Thus, you are NOT searching the web ________
You are searching a search engines database
Every result is at least a little bit “stale”
Check _________ Settings…
Slide 5:Your browser can contribute to “staleness,” too.
Keeps a database of web pages, too:
History
___________ Internet Files
“_______”
Faster to load a saved copy of a web page from _____________ than to retrieve a new copy of a web page from _____________
Check Browser Settings…
Slide 6:Coverage
60% of a search engine’s data appears in ___________ search engine’s database.
Only about 50% of a search engine’s data appears in “all” of the other search engines’ databases…
Thus, 40% of a search engine’s data does not appear in ___________ search engine’s database…
MORAL? Use one than one search engine…
Slide 7:e.g. Dogpile www.dogpile.com
Takes your search terms and searches ________________ for you…
_______-search engines
Slide 8:Ranking
Q: When you search and multiple (!) pages result, what determines which pages get listed first?
A: That search engine’s _________.
Slide 9:Common Ranking Schemes
____________
Many factors and algorithms
Number of times keywords of the search appear on the page
Word appears in title?
Word near top of page?
_____________
How many OTHER pages link to the page containing the desired search term(s) ?
A Combination of these two
Slide 10:Other Ranking Factors
“_____ for Rank”
Some search engines let you ___ for prominence…
“__________”
Tricking the ranking scheme into favoring your web pages…
Politics?
Google has begun censoring sites for Internet users in China who are searching the Web…
Slide 11:Key Searching Techniques
Slide 12:Phrases
Phrases in quotes
e.g. “calvin college”
Search on unique phrases
Proper nouns
“john calvin”
Slide 13:Boolean Operators
AND
Usually _____ when you list multiple terms
calvin college = calvin AND college
Slide 14:Boolean Operators
OR
Usually must be _______
Sometimes also must be in ________
Shakespeare AND (theatre OR theater)
for synonyms
Slide 15:Boolean Operators
_______! NOT
Calvin NOT hobbes
Google _______ sign: -
Calvin -hobbes
Slide 16:“_____ words”
Common words ______ by search engine
Google has _____ of them…
Solution?
Put in quotes – sometimes works
Better: preceed with a plus:
+who +are +you
Slide 17:Field Limiting - ____
Limit results to certain web page domain
____:
site:calvin.edu
site:.edu
Slide 18:Google
10 word limit
Indexes only first 101KB of a Web page
Slide 19:Yahoo!
Must __________ OR, AND, or AND NOT.
Also accepts parentheses
No 10-word limit.
Slide 20:Teoma
http://www.teoma.com
“Subject-Specific Popularity” ranking scheme
How many __________ pages reference the page
Optional follow-up steps after search results:
REFINE: suggested terms to add to your search
RESOURCES: communities, possibly directories, related to your search results
___________ database than Yahoo! And Google
Slide 21:__________ Pages
Search Engine Databases created by _________,
not by “web crawling” software
Thus, smaller databases, but _______ _______.
Examples:
LIBRARIANS' INDEX
http://www.lii.org
INFOMINE
http://infomine.ucr.edu
MEL (Michigan Elibrary)
http://www.mel.lib.mi.us
Academic Info
http://www.academicinfo.net
