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WHAT HAVE WE DONE SO FAR?WHAT HAVE WE DONE SO FAR?
Weeks 1 – 8 : various components of an Weeks 1 – 8 : various components of an information retrieval systeminformation retrieval system
Now – look at various examples of Now – look at various examples of information retrieval systemsinformation retrieval systems InternetInternet Digital libraryDigital library OPACOPAC Bibliographical systemsBibliographical systems
WMES3103 : WMES3103 : INFORMATION INFORMATION
RETRIEVALRETRIEVALWEEK 12WEEK 12
SEARCHING THE WEBSEARCHING THE WEB
INTERNETINTERNET
Different types of Different types of information on the information on the InternetInternet
Journal Journal magazines, magazines, newspapersnewspapers
DatabasesDatabases SoftwareSoftware MultimediaMultimedia Organisational Organisational
informationinformation
Different types of Web Different types of Web sitessites• EntertainmentEntertainment• Business & marketingBusiness & marketing• Reference/informationReference/information• NewsNews• Personal web sitesPersonal web sites
Information Source Information Source (http://www.clearinghouse.net)(http://www.clearinghouse.net)
Dictionaries & list of Dictionaries & list of acronymsacronyms
Telephone & email Telephone & email directorydirectory
EncyclopediaEncyclopedia ThesauriThesauri Dictionaries of Dictionaries of
other languagesother languages ArticlesArticles
E-jounalE-jounal Contents pages of Contents pages of
journalsjournals DirectoriesDirectories TV & radioTV & radio NewspaperNewspaper etcetc
WEBWEB
The Web is a portion of the InternetThe Web is a portion of the Internet Use of hypertextUse of hypertext 3 methods of searching for information on 3 methods of searching for information on
the Webthe WebUse a search engine Use a search engine Use a Web directory that classes the sites Use a Web directory that classes the sites
by subjectby subjectUse hyperlinkUse hyperlink
PROBLEMS WITH THE WEBPROBLEMS WITH THE WEB
DataData
a. Distributed dataa. Distributed data
b. High % of volatile datab. High % of volatile data
c. Large volumec. Large volume
d. Unstructured redundantd. Unstructured redundant
datadata
e. Quality of datae. Quality of data
f. Heterogeneous dataf. Heterogeneous data
PROBLEMS WITH THE WEBPROBLEMS WITH THE WEB
User’s interaction with the User’s interaction with the IRSIRS
a. How to specify a query?a. How to specify a query?
b. How to interpret the b. How to interpret the answer provided by the answer provided by the system?system?
SEARCH ENGINESSEARCH ENGINES
Single – use crawlers Single – use crawlers to find and retrieve to find and retrieve information, information, descriptors from own descriptors from own index database, use index database, use own database,own database,
ranking,ranking, (Altavista,Infoseek, (Altavista,Infoseek,
Excite,Goggle, Excite,Goggle, DirectHit, HotBot)DirectHit, HotBot)
• Specialised – Specialised – search for specific search for specific information only information only (Thomas, SOSIG, (Thomas, SOSIG, ERIC)ERIC)
• Meta – use other Meta – use other search engines search engines concurrently concurrently (Metacrawler, (Metacrawler, SavvySearch)SavvySearch)
USER INTERFACEUSER INTERFACE
Query interfaceQuery interface Basic : a box where Basic : a box where
user can type in one user can type in one or more wordsor more words
Complex – uses Complex – uses command language – command language – Boolean operators, Boolean operators, phrase searching, phrase searching, proximity searching, proximity searching, wild card - example : wild card - example : HotBot dan Northern HotBot dan Northern LightLight
ANSWER INTERFACEANSWER INTERFACE
Lists the 10 most relevant sites by rankingLists the 10 most relevant sites by ranking Ranking on the index and not on the textRanking on the index and not on the text Information – URL, size, date page was Information – URL, size, date page was
indexed, page indexed, title and a few lines indexed, page indexed, title and a few lines from the document or descriptors or a from the document or descriptors or a sentence sentence
Example : AltaVista, HotBot, Northern Light, Example : AltaVista, HotBot, Northern Light, ExciteExcite
Arranged by ranking and relevanceArranged by ranking and relevance Too many hits, resubmit queryToo many hits, resubmit query
WEB DIRECTORYWEB DIRECTORY
Numerous search engines provide Numerous search engines provide categorization of subjectscategorization of subjects
Also known as Also known as catalogscatalogs, , yellow pages yellow pages or or subject directoriessubject directories
Send web sites to the Web directory for Send web sites to the Web directory for checking and if accepted, it will be checking and if accepted, it will be classified and added to the directoryclassified and added to the directory
Example : YahooExample : Yahoo
USER - PROBLEMSUSER - PROBLEMS
Unable to search for wordsUnable to search for words Unable to find suitable words because do Unable to find suitable words because do
not understand how system look for the not understand how system look for the selected wordsselected words
Do not understand proper use of Boolean Do not understand proper use of Boolean operatorsoperators
EVALUATION OF WEB SITESEVALUATION OF WEB SITESCRITERIACRITERIA
AccuracyAccuracy AuthorityAuthority ObjectivityObjectivity CurrencyCurrency CoverageCoverage www.gvsu.edu/library/www.gvsu.edu/library/
TEN C’s FOR EVALUATING TEN C’s FOR EVALUATING INTERNET SOURCESINTERNET SOURCES
ContentContent CredibilityCredibility Critical thinkingCritical thinking CopyrightCopyright CitationCitation
ContinuityContinuity CensorshipCensorship ConnectivityConnectivity ComparabilityComparability ContextContext
www.uwec.edu/www.uwec.edu/library/guides/library/guides/tencs.htmltencs.html
METASEARCHERSMETASEARCHERS
Web servers which sends Web servers which sends query to a few search query to a few search engines, Web directories engines, Web directories and other databases, and other databases, collect and collate the collect and collate the answersanswers
Example : Metacrawler, Example : Metacrawler, Savvysearch, CopernicSavvysearch, Copernic
INTERNETINTERNET
An information retrieval systemAn information retrieval system Has input, process and outputHas input, process and output Has relevance feedback cycleHas relevance feedback cycle ComponentsComponents
Retrieval evaluationRetrieval evaluation Query language/operationQuery language/operation Text operationsText operations Indexing & searchingIndexing & searching User interfaceUser interface