SIMS 202Information Organization

and Retrieval

Prof. Marti Hearst and Prof. Ray LarsonUC Berkeley SIMS

Tues/Thurs 9:30-11:00amFall 2000

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 (by Ray Larson) 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

Cha-Cha System Architecture

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

Cha-Cha System Architecture

crawl theweb

store the

documents

create files of

metadata

Cheshire II

Cha-Cha System Architecture

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

Cha-Cha System Architecture

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

Cha-Cha System Architecture

Cheshire II

userquery

Cha-Cha System Architecture

Cheshire II

server accesses the

databases

Cha-Cha System Architecture

Cheshire II

results shownto user

Cha-Cha System Architecture

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.

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

Two Main Themes

Information Organization and

Design

Information Retrieval and the Search Process

Overview Example

Web site design– Incorporates many of the

organizational issues we will be covering

– Example taken from a study of professional designers, by Mark Newman

Adapted from slide by Mark Newman

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.)

Adapted from slide by Mark Newman

Design Specialties

Information Architecture– includes management

and more responsibility for content

User Interface Design– includes testing and

evaluation

Adapted from slide by Mark Newman

Web Site Design Process

Implementation

Design

Preliminary Design

Conceptualization

Needs Assessment

Adapted from slide by Mark Newman

Design Process: Preliminary Design

(information/navigation design: schematic)

Adapted from slide by Mark Newman

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

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– Might be a project, might be an exam (TBA)

Final exam Monday Dec 11 Grading:

– Assignments: 40%» Not evenly weighted

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

Readings

Course Reader– Will be available in about a week at Ned’s– (on Bancroft, across from the ASUC)

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 31.

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?