WHAT HAVE WE DONE SO FAR?  Weeks 1 – 8 : various components of an information retrieval system  Now – look at various examples of information retrieval systems  Internet  Digital library  OPAC  Bibliographical systems

WMES3103 : INFORMATION RETRIEVAL WEEK 12 SEARCHING THE WEB

INTERNET  Different types of information on the Internet  Journal magazines, newspapers  Databases  Software  Multimedia  Organisational information  Different types of Web sites Entertainment Business & marketing Reference/information News Personal web sites

Information Source (  Dictionaries & list of acronyms  Telephone & directory  Encyclopedia  Thesauri  Dictionaries of other languages  Articles  E-jounal  Contents pages of journals  Directories  TV & radio  Newspaper  etc

WEB  The Web is a portion of the Internet  Use of hypertext  3 methods of searching for information on the Web  Use a search engine  Use a Web directory that classes the sites by subject  Use hyperlink

PROBLEMS WITH THE WEB  Data a. Distributed data b. High % of volatile data c. Large volume d. Unstructured redundant data data e. Quality of data f. Heterogeneous data

PROBLEMS WITH THE WEB  User’s interaction with the IRS a. How to specify a query? a. How to specify a query? b. How to interpret the answer provided by the system? b. How to interpret the answer provided by the system?

SEARCH ENGINES  Single – use crawlers to find and retrieve information, descriptors from own index database, use own database,  ranking,  (Altavista,Infoseek, Excite,Goggle, DirectHit, HotBot) Specialised – search for specific information only (Thomas, SOSIG, ERIC) Meta – use other search engines concurrently (Metacrawler, SavvySearch)

USER INTERFACE  Query interface  Basic : a box where user can type in one or more words  Complex – uses command language – Boolean operators, phrase searching, proximity searching, wild card - example : HotBot dan Northern Light

ANSWER INTERFACE  Lists the 10 most relevant sites by ranking  Ranking on the index and not on the text  Information – URL, size, date page was indexed, page indexed, title and a few lines from the document or descriptors or a sentence  Example : AltaVista, HotBot, Northern Light, Excite  Arranged by ranking and relevance  Too many hits, resubmit query

WEB DIRECTORY Numerous search engines provide categorization of subjects  Also known as catalogs, yellow pages or subject directories  Send web sites to the Web directory for checking and if accepted, it will be classified and added to the directory  Example : Yahoo

USER - PROBLEMS  Unable to search for words  Unable to find suitable words because do not understand how system look for the selected words  Do not understand proper use of Boolean operators

EVALUATION OF WEB SITES CRITERIA  Accuracy  Authority  Objectivity  Currency  Coverage 

TEN C’s FOR EVALUATING INTERNET SOURCES  Content  Credibility  Critical thinking  Copyright  Citation  Continuity  Censorship  Connectivity  Comparability  Context  /guides/tencs.html

METASEARCHERS  Web servers which sends query to a few search engines, Web directories and other databases, collect and collate the answers  Example : Metacrawler, Savvysearch, Copernic

INTERNET  An information retrieval system  Has input, process and output  Has relevance feedback cycle  Components  Retrieval evaluation  Query language/operation  Text operations  Indexing & searching  User interface