计算机检索基础课件

计算机信息检索ComputerizedInformationRetrieval

（工程硕士）

2004.91信息检索词汇（terms）Informationretrieval(IR)Informationaccess(obtain)Informationsearch(lookfor)Informationsearching(lookfor)Informationseeking(focusonusers,active)locatehit21.信息检索发展阶段●手工操作(manual)●计算机化(computerized)●网络化(networked)●智能化(intelligentized)●认知化(cognized)What’ssearchinglike?“Findinganeedleinahaystack”3

通信网络联机检索中心

检索终端数据库2.1联机检索(onlinesearch)

Theprocessoflocatingspecificpiecesofinfofromoneormoredatabasesthatresideonthecomputers(hosts).Thesearchisatrueinteractionbetweenyouandsearchsystem.

主机

Feature:interaction,realtimeremote,DirectInternetWAN微机5OnlinedatabasesFeatures

¨Atest-bedforearlyIRexperiments&development

¨TheshowcaseofIRtechnology(e.g,relevanceretrieval)untiltheInternet,theWebbecamepopular

¨AlaboratoryforacquiringinformationretrievalskillsIRcapability

¨Coversvirtuallyeverytypeofdatabasestructures

¨Implementalldifferentretrievalmodelsandtechniques-----Hahn6OPACs

Features

¨AnextensionofMARCrecords

¨Aproductoflibraryautomation

¨Abibliographicdatabaseoflibraryresourcesforaninstitutionatvariouslevels,e.g,local,regional,national

IRcapability

¨

Easytobrowse(resembleshelfstructure)

¨Basedonwell-establishedhierarchicaldatabasestructure¨Mayprovidesophisticatedsearchingcapabilitiesbutusersmaynotbenefitfromthem7

检索终端局域网

服务器

光驱

LAN微机towerjukebox光盘联机检索(CD

online))9CD-ROMs

Features

¨OnlinedatabasesinCD-ROMmedium

¨Portability¨Cheaper&moreconvenientaccessuntiltheWebbecomesthegatewayforCD-ROMaccess

¨Noticeableprobleminupdatingthedatabase¨

HypertextorhypermediaisheavilyusedinCD-ROM

¨Becominganobsoletetechnology?IRcapabilities

¨Introducethe

browsingfeature

¨OtherIRtechniquessimilartothoseofonlinedatabases

¨

Slowerinspeed102.3网络信息检索（TheInternet）

Features

¨InitialintentionwasmoreonresourcessharingthanIR

¨Rapiddevelopmentandconstantimprovement

¨Wideusage

¨Goodforpresentinginformation,lesssofororganizingformation

IRcapability

¨

Retrievalcapabilityisanaddition,notincludedintheoriginaldesignforthesystemexceptinthecaseofWAIS¨Quality(unevenretrievalperformance)andquantityvaryfromonetooltoanother¨

Replacingonlinesystemsandbecomingthelab&showcasefornew,advancedandsophisticatedIRtechniques113.数据库的基本概念

3.1数据库的类型

(1)参考数据库书目数据(bibliographicdatabase)目录数据库(catalogdatabase)文摘索引数据库(abstract/indexdatabase) 指南数据库(directorydatabase)

13(2)源数据库(sourcedatabase,databank)数值数据库（numericdatabase）文本-数值数据库（text-numericdatabase）属性数据库（propertydatabase）术语数据库（terminologybank）全文数据库（full-textdatabase）图象数据库（graphicdatabase）多媒体数据库（multimediadatabase）…143.2书目数据库的结构

文档(file)

数据库组织的基本形式记录(record)

文档的构成单位

(对应一个书目条目)154.计算机检索基本方法

4.1.检索策略

检索步骤的科学安排

4.2.检索步骤

17确定检索点/词

检索课题用户

主题分析选择检索系统

选择数据库制定检索式

计算机处理

结果检验

词表NY18

内容Content范围Coverage时效Currency费用Cost选库的4C原则:19

检索词/语言:非规范词(非受控词自由词) uncontrolled,free-term规范词(受控词)controlled

汉语主题词表(中文)LCSH词表(英文)

21

禁用词:Stopwords:在记录中出现的频度太高，而不能用以检索。如：AAREFOROFTHEWITHANASFORMONTHISWOULDANDBYINTHATTO,…22

4.3检索方法

(1)命令检索(commandsearch)算符(operator)检索式(query,statement,formula,profile)(2)菜单检索(menusearch)菜单选择(menuselectio