ITIS 1210 Introduction to Web-Based Information Systems Chapter 27 How Internet Searching Works.

ITIS 1210ITIS 1210Introduction to Web-Based Introduction to Web-Based

Information SystemsInformation Systems

Chapter 27Chapter 27How Internet Searching WorksHow Internet Searching Works

IntroductionIntroduction

Major advantage of InternetMajor advantage of Internet HUGE amounts of information availableHUGE amounts of information available

Major DISadvantage:Major DISadvantage: It’s DISORGANIZEDIt’s DISORGANIZED There is no central ownership so there’sThere is no central ownership so there’s

No common filing systemNo common filing system No “Dewey Decimal System”No “Dewey Decimal System”

No common glossaryNo common glossary


I think the book confuses these two terms I think the book confuses these two terms but …but …

Two popular solutionsTwo popular solutions IndexesIndexes Search EnginesSearch Engines

IndexesIndexes Provide a lookup mechanismProvide a lookup mechanism Associate lookup terms with informationAssociate lookup terms with information

Example: telephone bookExample: telephone book


On the Web, indexes tend to be On the Web, indexes tend to be hierarchicalhierarchical Click on a clickClick on a click Takes you to a list of sub-categoriesTakes you to a list of sub-categories May be several levels deepMay be several levels deep At some point documents associated with that At some point documents associated with that

category become availablecategory become available Yahoo! For exampleYahoo! For example

Binary search!Binary search!


Yahoo!Yahoo!


Search engines are massive databasesSearch engines are massive databases Don’t present information in a hierarchical Don’t present information in a hierarchical

formform InsteadInstead

You provide search termYou provide search term Database returns relevant resultsDatabase returns relevant results

Confusion results from fact that database Confusion results from fact that database are organized around indexesare organized around indexes


Google tends to be the default search Google tends to be the default search engineengine Big mistake, other ones out there, some Big mistake, other ones out there, some

betterbetter

Have three basic characteristicsHave three basic characteristics Spider – gathers information from WebSpider – gathers information from Web Database – Stores that informationDatabase – Stores that information Search tool – Lets users search the databaseSearch tool – Lets users search the database


Spiders work constantlySpiders work constantly Retrieving information from Web sitesRetrieving information from Web sites Presenting it to search engine for analysisPresenting it to search engine for analysis

Engines characterize the dataEngines characterize the data Remember, HTML is basically just text filesRemember, HTML is basically just text files By keyword in documentBy keyword in document

Some use all, some only a fewSome use all, some only a few By entire content of documentBy entire content of document

By size, title, heading, metadata, etc.By size, title, heading, metadata, etc.


Results from this analysis stored in Results from this analysis stored in databasedatabase Typically keyword & URLTypically keyword & URL Other information might be stored as wellOther information might be stored as well

First few sentences on Web pageFirst few sentences on Web page Last date updatedLast date updated

Search tool provides access to database Search tool provides access to database for usersfor users


User provides keyword (or other search User provides keyword (or other search term)term)

Tool returns list of data in database that Tool returns list of data in database that fits that termfits that term

Different search engines return results in Different search engines return results in different waysdifferent ways Weigh resultsWeigh results Sponsored linksSponsored links


No search engine indexes the entire No search engine indexes the entire InternetInternet

All have strengths and weaknessesAll have strengths and weaknesses Limiting your self to a single search engine Limiting your self to a single search engine

is is Intellectually lazyIntellectually lazy Academically short-sightedAcademically short-sighted Ultimately self-defeatingUltimately self-defeating

Would you only shop at Wal-Mart?Would you only shop at Wal-Mart?

How Internet Search Engines WorkHow Internet Search Engines Work

Spiders are just programsSpiders are just programs They follow a link to a Web pageThey follow a link to a Web page

Really, the Web page Really, the Web page comes to themcomes to them

Different spiders follow different rulesDifferent spiders follow different rules Written by different programmers for different Written by different programmers for different

companiescompanies Follow every linkFollow every link Ignore links to graphics files or newsgroupsIgnore links to graphics files or newsgroups


Content analyzed and stored in databaseContent analyzed and stored in database Indexes are built and updatedIndexes are built and updated

Users visit search engine siteUsers visit search engine site Provide search termProvide search term

Describes the information you wantDescribes the information you want Might ask to match keyword(s)Might ask to match keyword(s) Might be to limit byMight be to limit by

DateDate Type of fileType of file SizeSize


Search engine softwareSearch engine software Searches database for information matching Searches database for information matching

keywordskeywords Results formatted as a Web page in HTMLResults formatted as a Web page in HTML Sent back to userSent back to user

How Meta-Search Software WorksHow Meta-Search Software Works

ProblemProblem Web is too large for any one search engine to Web is too large for any one search engine to

consistently provide superior resultsconsistently provide superior results Best approach is a combination of results Best approach is a combination of results

from multiple search enginesfrom multiple search engines

Meta-search software lets you search Meta-search software lets you search multiple search engines for resultsmultiple search engines for results

Better than searching each one Better than searching each one individuallyindividually


Some software uses multiple “agents”Some software uses multiple “agents” Specialized software that does one thing very Specialized software that does one thing very

well – like searchingwell – like searching

Each agent contacts a single search Each agent contacts a single search engineengine

The agents know how each engine The agents know how each engine functionsfunctions How to ask the right questionHow to ask the right question


Individual search engines report their Individual search engines report their results to the agentresults to the agent

Agents report results back to meta-search Agents report results back to meta-search engineengine

This process may be repeated multiple This process may be repeated multiple times by each agenttimes by each agent


Meta-search engine deletes duplicate Meta-search engine deletes duplicate resultsresults May rank based on how many search engines May rank based on how many search engines

report a specific sitereport a specific site One indication of quality – lots of referencesOne indication of quality – lots of references

You see a result you like, click on the link, You see a result you like, click on the link, and are taken to that Web pageand are taken to that Web page


No two meta-search engines are alikeNo two meta-search engines are alike Some only refer to popular search enginesSome only refer to popular search engines Some include lesser-known search Some include lesser-known search

engines, newsgroups, or databaseengines, newsgroups, or database Also differ on how results are presentedAlso differ on how results are presented

Some indicate which search engine returned Some indicate which search engine returned results, some don’tresults, some don’t

LinksLinks

http://www.dmoz.org/Computers/Internet/http://www.dmoz.org/Computers/Internet/Searching/Metasearch//Searching/Metasearch//

LinksLinks

http://www.lib.berkeley.edu/TeachingLib/http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/MetaSearch.htmlGuides/Internet/MetaSearch.html

http://news.zdnet.com/2100-9588_22-http://news.zdnet.com/2100-9588_22-5647280.html5647280.html

http://www.dmoz.org/Computers/Internet/http://www.dmoz.org/Computers/Internet/Searching/Metasearch//Searching/Metasearch//

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ITIS 1210 Introduction to Web-Based Information Systems Chapter 27 How Internet Searching Works.

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