search engine 1 - copy

7/29/2019 Search Engine 1 - Copy

1/19

Tefko Saracevic 1

Search Engines


2/19

Tefko Saracevic 2

Definition

SearchCOMPUTING (transitive verb) to examine a computer file,

disk, database, or network for particular information

Enginesomething that supplies the driving force or energy to a

movement, system, or trend

Search Enginea computer program that searches for particular keywords

and returns a list of documents in which they were found,especially a commercial service that scans documents onthe Internet


3/19

Tefko Saracevic 3

Brief History

Very First tool used for searching wasArchie created in 1990.

Aliweb was next to come in 1993 which usedthe crawler.

Web crawler and Lycos were next to come in1994.


4/19

Tefko Saracevic 4

Your

Browser

How Search Engines Work

The Web

URL1

URL2

URL3 URL4

Crawler

Indexer

SearchEngine

Database Eggs?Eggs.

Eggs - 90%

Eggo - 81%

Ego- 40%

Huh? - 10%

All AboutEggsby

S. I. Am


5/19

Tefko Saracevic 5

Ways of Searching

Keyword searching

Refined Searching

Relevancy Rankings

Information on meta tags

Concept based Searching


6/19

Tefko Saracevic 6

Few Search Engines

AltaVista (www.altavista.com)

Excite (www.excite.com)

Infoseek (www.go.com) Lycos (www.lycos.com)

HotBot (www.hotbot.com)

Yahoo (www.yahoo.com) Google (www.google.com)
http://www.altavista.com/http://www.excite.com/http://www.go.com/http://www.lycos.com/http://www.hotbot.com/http://www.yahoo.com/http://www.google.com/http://www.google.com/http://www.yahoo.com/http://www.hotbot.com/http://www.lycos.com/http://www.go.com/http://www.excite.com/http://www.altavista.com/


7/19 Tefko Saracevic 7

Web Crawler

Create a copy of all visited pages for laterprocessing by a search engine.

used for automating maintenance taskson a website, such as checking links orvalidating HTML code



can be used to gather specific types ofinformation from Web pages, such as

harvesting e-mail addresses (usually forspam).

for a number of reasons crawlers

cover only a fraction, not cover-invisibleweb.
http://en.wikipedia.org/wiki/Spamminghttp://en.wikipedia.org/wiki/Spamming



Indexing

Search engine Indexing collects, parses, and storesdata to facilitate fast and accurate information

retrieval. The purpose of storing an index is to optimize speed

and performance in finding relevant documents for a

search query.

Without an index, the search engine would scan everydocument in the corpus, which would requireconsiderable time and computing power.



elaborationsimilarities, differences

all search engines have these basic parts incommon

BUT the actual processes methods howthey do it are based on various algorithms& they differ

most are proprietary with details kept mostly

secret but based on well known principles frominformation retrieval or classification

to some extent Google is an exception theypublished their method



Case of

developed by Sergey Brin and Lawrence Page whilestudents at Stanford in the beginning run on Stanford computers

basic approach has been described in their famous

paperThe Anatomy of a Large-Scale HypertextualWeb Search Engine well written, simple language, has their pictures

in acknowledgement they cite the support by NSFs DigitalLibrary Initiative i.e. initially, Google came out ofgovernment sponsored research

describe their method PageRank - based on rankinghyperlinks as in citation indexing

We chose our system name, Google, because it is acommon spelling of googol, or ten on hundredth power
http://www-db.stanford.edu/~backrub/google.htmlhttp://www-db.stanford.edu/~backrub/google.htmlhttp://www-db.stanford.edu/~backrub/google.htmlhttp://www-db.stanford.edu/~backrub/google.htmlhttp://www-db.stanford.edu/~backrub/google.htmlhttp://www-db.stanford.edu/~backrub/google.htmlhttp://www-db.stanford.edu/~backrub/google.html



Coverage Differences

no engine covers more than a fraction ofWWW

estimates: none more than 16%

hard (even impossible) to discern & comparecoverage, but they differ substantially inwhat they cover



o in addition:

many national search engines

own coverage, orientation,

governance

many specialized or domain searchengines

own coverage geared to subject ofinterest

many comprehensive sources

independent


14/19

Tefko Saracevic 14

Advantages of search engine

Search vast databases

Very easy to use

Sophisticated searching often available

Normally global


15/19

Tefko Saracevic 15

Limitations

Automated method of collecting informationsrather crude.

Information may be out of context .

May produce out of date sites.


16/19

Tefko Saracevic 16

Search engines are also many timesvictims of spamdexing.

use of techniques that pushrankings higher than they belong isalso called spamdexing.

methods typically include textual

as well as link-based techniques.


17/19

Tefko Saracevic 17

Search Engine Optimization

(SEO) SEO is one of the key Web Marketing activities.

It is a part of search engine marketing.

SEO + SEM = PPC(pay par click)

When any user search on Google, on the right side,display some adds on right side under Sponsor Linkssection, these are called Pay Per Click adds.
http://en.wikipedia.org/wiki/Web_Marketinghttp://en.wikipedia.org/wiki/Web_Marketinghttp://en.wikipedia.org/wiki/Web_Marketinghttp://en.wikipedia.org/wiki/Web_Marketing


18/19

Tefko Saracevic 18


19/19

Tefko Saracevic 19

Thank you

search engine 1 - copy

Documents