8/28/2001Information Organization and Retrieval SIMS 202 Information Organization and Retrieval Prof. Ray Larson & Prof. Warren Sack UC Berkeley SIMS Tues/Thurs

8/28/2001 Information Organization and Retrieval

SIMS 202Information Organization

and Retrieval

Prof. Ray Larson & Prof. Warren SackUC Berkeley SIMS

Tues/Thurs 10:30-12:00 amFall 2001

Lecture authors: Marti Hearst & Ray Larson


Today

• Introductions

• Course Overview

• Administrivia


Goals of the Course

• Learn about:– Design, development and use of information

storage and retrieval systems– Practical and theoretical foundations of

information organization and analysis– Evaluation of information access systems– Cognitive and user-centric considerations– Hands-on experience with information systems


Two Main Themes

Information Organization and

Design

Information Retrieval and the Search Process


Web Search Questions

• What do people search for?

• How do people use search engines?– How often do people find what they are looking

for? – How difficult is it for people to find what they

are looking for?

• How can search engines be improved?


What Do People Search for on the Web?

• Study by Spink et al., Oct 98– www.shef.ac.uk/~is/publications/infres/paper53.html

– Survey on Excite, 13 questions– Data for 316 surveys


What Do People Search for on the Web?

Topics• Genealogy/Public Figure: 12%• Computer related: 12%• Business: 12%• Entertainment: 8%• Medical: 8%• Politics & Government 7%• News 7%• Hobbies 6%• General info/surfing 6%• Science 6%• Travel 5%• Arts/education/shopping/images 14%

Something is missing…


What do people search for on the web?

• 4660 sex• 3129 yahoo• 2191 internal site

admin check from kho• 1520 chat• 1498 porn• 1315 horoscopes• 1284 pokemon• 1283 SiteScope test

• 1223 hotmail• 1163 games• 1151 mp3• 1140 weather• 1127 www.yahoo.com• 1110 maps• 1036 yahoo.com• 983 ebay• 980 recipes

50,000 queries from excite 1997 Most frequent terms:


Why do these differ?

• Self-reporting survey

• The nature of language– Only a few ways to say certain things– Many different ways to express most concepts

• UFO, Flying Saucer, Space Ship, Satellite

• How many ways are there to talk about history?


Intranet Queries (Aug 2000)• 3351 bearfacts• 3349 telebears• 1909 extension• 1874 schedule+of+classes• 1780 bearlink• 1737 bear+facts• 1468 decal• 1443 infobears• 1227 calendar• 989 career+center• 974 campus+map• 920 academic+calendar• 840 map

• 773 bookstore• 741 class+pass• 738 housing• 721 tele-bears• 716 directory• 667 schedule• 627 recipes• 602 transcripts• 582 tuition• 577 seti• 563 registrar• 550 info+bears• 543 class+schedule• 470 financial+aid


Intranet Queries• Summary of sample data from 3 weeks of UCB queries

– 13.2% Telebears/BearFacts/InfoBears/BearLink (12297)

– 6.7% Schedule of classes or final exams (6222)

– 5.4% Summer Session (5041)

– 3.2% Extension (2932)

– 3.1% Academic Calendar (2846)

– 2.4% Directories (2202)

– 1.7% Career Center (1588)

– 1.7% Housing (1583)

– 1.5% Map (1393)

• Average query length over last 4 months: 1.8 words

• This suggests what is difficult to find from the home page


An Example Search System:Cha-Cha

• A system for searching complex intranets

• Places retrieval results in context


An Example Search System: Cha-Cha

• Important design goals:– Users at any level of computer expertise

– Browsers at any version level

– Computers of any speed




Search: Where to Start?• Guess words?

– Search engine plunges you into the middle of a site/collection

– Too many or too few results– No context

• Use a directory?– If large, may be difficult/frustrating to navigate– Several ways to organize the information– May not reflect users’ needs

• Solution: Integrate Browsing and Search




How Cha-Cha Works• Crawl entire Intranet• Compute the shortest hyperlink path from a certain root

page to every web page• Index and compute metadata for the pages

– Using Cheshire II – Run a user query.– Gather all the hits– Create a “directory” based on combining the shortest paths– Special graph algorithm removes redundant links and internal

nodes


Cha-Cha System Architecture

crawl theweb

store the

documents



crawl theweb

store the

documents

create files of

metadata

Cheshire II


Cha-Cha Metadata

• Information about web pages– Title– Length– Inlinks– Outlinks– Shortest Paths from a root home page

• Used to provide innovative search interface



crawl theweb

store the

documents

create files of

metadata

Cheshire II



crawl theweb

create a keyword

index

store the

documents

create files of

metadata

Cheshire II


Creating a Keyword Index

• For each document– Tokenize the document

• Break it up into tokens: words, stems, punctuation

• There are many variations on this

– Record which tokens occurred in this document• Called an Inverted Index

• Dictionary: a record of all the tokens in the collection and their overall frequency

• Postings File: a list recording for each token, which document it occurs in and how often it occurs



Cheshire II

userquery


Responding to the User Query

• User searches on “pam samuelson”

• Search Engine looks up documents indexed with one or both terms in its inverted index

• Search Engine looks up titles and shortest paths in the metadata index

• User Interface combines the information and presents the results as HTML



Cheshire II

userquery



Cheshire II

server accesses the

databases



Cheshire II

results shownto user



Cheshire II

results shownto user

server accesses the

databases

userquery


What hasn’t been explained here?

• How documents are ranked

• How queries are formed

• How shortest paths are computed

• How the system is built– … among other things!– This is just an introduction! Much more later.


Two Main Themes

Information Organization and

Design

Information Retrieval and the Search Process


(Approximate) Course Schedule• Retrieval

– The Search Process– Content Analysis

• Tokenization, Zipf’s Law, Lexical Associations

– IR Implementation– Term weighting and

document ranking• Vector space model• Probabilistic model

– User Interfaces• Overviews, query

specification, providing context, relevance feedback


Overview Example

• Web site design/ Information Architecture– Incorporates many of the organizational issues

we will be covering– Example taken from a study of professional

designers, by Mark Newman

Information Organization and Retrieval

Information Architecture and Web Site Design

• Information design– structure, categories of

information

• Navigation design– interaction with information

structure

• Graphic design– visual presentation of

information and navigation (color, typography, etc.)


Design Specialties• Information Architecture

– includes management and more responsibility for content

• User Interface Design– includes testing and

evaluation


Web Site Design Process

Implementation

Design

Preliminary Design

Conceptualization

Needs Assessment


Design Process: Preliminary Design

(information/navigation design: schematic)


Design Process: Preliminary Design

(navigation design: storyboard)

Web Site Design Process

• Major design activities are:– Deciding on a set of categories that define the information

content– Deciding how to represent these– Deciding on the navigation structure through the

categorized content• Example: a movie listing website

• There are similarities and differences to:– Database design– Thesaurus design


(Approximate) Course Schedule

• Organization– Overview

– Metadata and Markup

– Controlled Vocabularies, Classification, Thesauri

– Information Design• Thesaurus Design

• Database Design


Assignments and Exams• Approximately 9 short assignments (due within

one week – ten days)– Sometimes “checked”, sometimes graded

• One Midterm exam (take-home open book)• Final exam (during Finals week)• Grading:

– Assignments: 40%• Not evenly weighted

– Final: 25%– Midterm: 25%– Class Participation: 10%


Readings

• Course Reader– Will be available in about a week (will announce)

– Textbooks• Modern Information Retrieval, Baeza-Yates and Ribiero-Neto

(Eds.), Addison Wesley, 1999

• The Organization of Information, Arlene G. Taylor, Libraries Unlimited, 1999,


Homework (!)

• Read the handout (Borges and Dennett)• Write one or two paragraphs on

– What is information, according to your background or area of expertise?

• Due in class this Thursday, Aug 30.


What is Information?

• There is no “correct” definition• Can involve philosophy, psychology, signal processing,

physics • Cookie Monster’s definition:

– “news or facts about something”

• Oxford English Dictionary– information: informing, telling; thing told, knowledge, items of

knowledge, news– knowledge: knowing familiarity gained by experience; person’s

range of information; a theoretical or practical understanding of; the sum of what is known


Next Time

More on What is Information?And How much of it is out there?

Documents

8/28/2001Information Organization and Retrieval SIMS 202 Information Organization and Retrieval Prof. Ray Larson & Prof. Warren Sack UC Berkeley SIMS Tues/Thurs