Transcript 幻灯片 1 - Peking University

Information Extraction
PengBo
Dec 2, 2010
Topics of today


IE: Information Extraction
Techniques



Wrapper Induction
Sliding Windows
From FST to HMM
What is IE?
Example: The Problem
Martin Baker, a person
Genomics job
Employers job posting form
Example: A Solution
Extracting Job Openings from the Web
foodscience.com-Job2
JobTitle: Ice Cream Guru
Employer: foodscience.com
JobCategory: Travel/Hospitality
JobFunction: Food Services
JobLocation: Upper Midwest
Contact Phone: 800-488-2611
DateExtracted: January 8, 2001
Source: www.foodscience.com/jobs_midwest.htm
OtherCompanyJobs: foodscience.com-Job1
Job Openings:Category = Food Services
Keyword = Baker
Location = Continental U.S.
Data Mining the Extracted Job Information
Two ways to manage information
“ceremonial soldering”
Query
Answer
Xxx xxxx
xxxx xxx
xxx xxx
xx xxxx
xxxx xxx
X:advisor(wc,Y)&affil(X,lti) ?
Query
Xxx xxxx
xxxx
xxxxxxx
Xxx
xxxxxxx
xxx xxx
xx xxxx
xxxXxx
xxx xxxx
xxxx
xxxx
xxx
xx xxxx xxx
xxx
xxx
xxxx
xxx
xx xxxx
xxxx xxx
Answer
inference
retrieval
Xxx xxxx
xxxx xxx
xxx xxx
xx xxxx
xxxx xxx
{X=em; X=vc}
Xxx xxxx
xxxx
xxxxxxx
Xxx
xxxxxxx
xxx
xxxxxxx
Xxx
xx xxxx
xxxxxxx
xxx xxx
xxxx
xxxxx
xxxx
xxx xxx
xxxx
xxxxx
xxxx
xxxx xxx
Xxx xxxx
xxxx xxx
xxx xxx
xx xxxx
xxxx xxx
advisor(wc,vc)
advisor(yh,tm)
IE
affil(wc,mld)
affil(vc,lti)
fn(wc,``William”)
fn(vc,``Vitor”)
AND
What is Information Extraction?

Recovering structured data from formatted
text
What is Information Extraction?

Recovering structured data from formatted
text

Identifying fields (e.g. named entity recognition)
What is Information Extraction?

Recovering structured data from formatted
text


Identifying fields (e.g. named entity recognition)
Understanding relations between fields (e.g. record
association)
What is Information Extraction?

Recovering structured data from formatted
text



Identifying fields (e.g. named entity recognition)
Understanding relations between fields (e.g. record
association)
Normalization and deduplication
What is Information Extraction?

Recovering structured data from formatted
text




Identifying fields (e.g. named entity recognition)
Understanding relations between fields (e.g. record
association)
Normalization and deduplication
Today, focus mostly on field identification &
a little on record association
Applications
IE from Research Papers
Chinese Documents regarding
Weather
Chinese Academy of Sciences
200k+ documents
several millennia old
- Qing Dynasty Archives
- memos
- newspaper articles
- diaries
Wrapper Induction
“Wrappers”

If we think of things from the database point of
view



We want to be able to database-style queries
But we have data in some horrid textual form/content
management system that doesn’t allow such querying
We need to “wrap” the data in a component that
understands database-style querying
 Hence the term “wrappers”



Title: Schulz and Peanuts: A Biography
Author: David Michaelis
List Price: $34.95
Wrappers:
Simple Extraction Patterns

Specify an item to extract for a slot using a regular
expression pattern.


Price pattern: “\b\$\d+(\.\d{2})?\b”
May require preceding (pre-filler) pattern and
succeeding (post-filler) pattern to identify the end of
the filler.

Amazon list price:
 Pre-filler pattern: “<b>List Price:</b> <span class=listprice>”
 Filler pattern: “\b\$\d+(\.\d{2})?\b”
 Post-filler pattern: “</span>”
Wrapper tool-kits

Wrapper toolkits


Specialized programming environments for writing &
debugging wrappers by hand
Some Resources
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
Wrapper Development Tools
LAPIS
Wrapper Induction


Problem description:
Task: learn extraction rules based on labeled
examples


Hand-writing rules is tedious, error prone, and time
consuming
Learning wrappers is wrapper induction
Induction Learning

Rule induction:


INPUT:




formal rules are extracted from a set of observations.
The rules extracted may represent a full scientific
model of the data, or merely represent local patterns
in the data.
Labeled examples: training & testing data
Admissible rules (hypotheses space)
Search strategy
Desired output:

Rule that performs well both on training and testing
data
Wrapper induction
Highly regular
source documents


Relatively simple
extraction patterns

Efficient
learning algorithm

Build a training set of
documents paired with
human-produced filled
extraction templates.
Learn extraction
patterns for each slot
using an appropriate
machine learning
algorithm.
Goal: learn from a
human teacher how
to extract certain
database records
from a particular
web site.
User gives first K positive—and
thus many implicit negative
examples
Learner
Kushmerick’s WIEN system


Earliest wrapper-learning system (published
IJCAI ’97)
Special things about WIEN:

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Treats document as a string of characters
Learns to extract a relation directly, rather than
extracting fields, then associating them together in
some way
Example is a completely labeled page
WIEN system: a sample wrapper
Learning LR wrappers
labeled pages
<HTML><HEAD>Some Country Codes</HEAD>
<B>Congo</B>
<I>242</I><BR>
<HTML><HEAD>Some
Country Codes</HEAD>
<B>Egypt</B>
<I>20</I><BR>
<B>Congo</B>
<I>242</I><BR>
<HTML><HEAD>Some
Country Codes</HEAD>
<B>Belize</B>
<I>501</I><BR>
<B>Egypt</B>
<I>20</I><BR>
<B>Congo</B>
<I>242</I><BR>
<HTML><HEAD>Some
Country Codes</HEAD>
<B>Spain</B>
<I>34</I><BR>
<B>Belize</B>
<I>501</I><BR>
<B>Egypt</B>
<I>20</I><BR>
<B>Congo</B>
<I>242</I><BR>
</BODY></HTML>
<B>Spain</B>
<I>34</I><BR>
<B>Belize</B>
<I>501</I><BR>
<B>Egypt</B>
<I>20</I><BR>
</BODY></HTML>
<B>Spain</B>
<I>34</I><BR>
<B>Belize</B>
<I>501</I><BR>
</BODY></HTML>
<B>Spain</B> <I>34</I><BR>
</BODY></HTML>
wrapper
l1, r1, …, lK, rK
Example: Find 4 strings
<B>, </B>, <I>, </I>
 l1 ,
r1 ,
l2 ,
r2 
LR wrapper
Left delimiters L1=“<B>”, L2=“<I>”; Right R1=“</B>”, R2=“</I>”
LR: Finding r1
<HTML><TITLE>Some Country Codes</TITLE>
<B>Congo</B> <I>242</I><BR>
<B>Egypt</B> <I>20</I><BR>
<B>Belize</B> <I>501</I><BR>
<B>Spain</B> <I>34</I><BR>
</BODY></HTML>
LR: Finding l1, l2 and r2
<HTML><TITLE>Some Country Codes</TITLE>
<B>Congo</B> <I>242</I><BR>
<B>Egypt</B> <I>20</I><BR>
<B>Belize</B> <I>501</I><BR>
<B>Spain</B> <I>34</I><BR>
</BODY></HTML>
WIEN system

Assumes items are always in fixed, known
order



… Name: J. Doe; Address: 1 Main; Phone: 111-1111. <p>
Name: E. Poe; Address: 10 Pico; Phone: 777-1111. <p> …
Introduces several types of wrappers

LR
Learning LR extraction rules

Admissible rules:
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
prefixes & suffixes of items of interest
Search strategy:

start with shortest prefix & suffix, and expand until
correct
Summary of WIEN

Advantages:


Fast to learn & extract
Drawbacks:



Cannot handle permutations and missing items
Must label entire page
Requires large number of examples
Sliding Windows
Extraction by Sliding Window
GRAND CHALLENGES FOR MACHINE LEARNING
Jaime Carbonell
School of Computer Science
Carnegie Mellon University
E.g.
Looking for
seminar
location
3:30 pm
7500 Wean Hall
Machine learning has evolved from obscurity
in the 1970s into a vibrant and popular
discipline in artificial intelligence
during the 1980s and 1990s.
As a result
of its success and growth, machine learning
is evolving into a collection of related
disciplines: inductive concept acquisition,
analytic learning in problem solving (e.g.
analogy, explanation-based learning),
learning theory (e.g. PAC learning),
genetic algorithms, connectionist learning,
hybrid systems, and so on.
CMU UseNet Seminar Announcement
Extraction by Sliding Window
GRAND CHALLENGES FOR MACHINE LEARNING
Jaime Carbonell
School of Computer Science
Carnegie Mellon University
E.g.
Looking for
seminar
location
3:30 pm
7500 Wean Hall
Machine learning has evolved from obscurity
in the 1970s into a vibrant and popular
discipline in artificial intelligence
during the 1980s and 1990s.
As a result
of its success and growth, machine learning
is evolving into a collection of related
disciplines: inductive concept acquisition,
analytic learning in problem solving (e.g.
analogy, explanation-based learning),
learning theory (e.g. PAC learning),
genetic algorithms, connectionist learning,
hybrid systems, and so on.
CMU UseNet Seminar Announcement
Extraction by Sliding Window
GRAND CHALLENGES FOR MACHINE LEARNING
Jaime Carbonell
School of Computer Science
Carnegie Mellon University
E.g.
Looking for
seminar
location
3:30 pm
7500 Wean Hall
Machine learning has evolved from obscurity
in the 1970s into a vibrant and popular
discipline in artificial intelligence
during the 1980s and 1990s.
As a result
of its success and growth, machine learning
is evolving into a collection of related
disciplines: inductive concept acquisition,
analytic learning in problem solving (e.g.
analogy, explanation-based learning),
learning theory (e.g. PAC learning),
genetic algorithms, connectionist learning,
hybrid systems, and so on.
CMU UseNet Seminar Announcement
Extraction by Sliding Window
GRAND CHALLENGES FOR MACHINE LEARNING
Jaime Carbonell
School of Computer Science
Carnegie Mellon University
E.g.
Looking for
seminar
location
3:30 pm
7500 Wean Hall
Machine learning has evolved from obscurity
in the 1970s into a vibrant and popular
discipline in artificial intelligence
during the 1980s and 1990s.
As a result
of its success and growth, machine learning
is evolving into a collection of related
disciplines: inductive concept acquisition,
analytic learning in problem solving (e.g.
analogy, explanation-based learning),
learning theory (e.g. PAC learning),
genetic algorithms, connectionist learning,
hybrid systems, and so on.
CMU UseNet Seminar Announcement
A “Naïve Bayes” Sliding Window
Model
[Freitag 1997]
…
00 : pm Place : Wean Hall Rm 5409 Speaker : Sebastian Thrun …
w t-m
w t-1 w t
w t+n
w t+n+1
w t+n+m
prefix
contents
suffix
Estimate Pr(LOCATION|window) using Bayes rule
Try all “reasonable” windows (vary length, position)
Assume independence for length, prefix words, suffix words, content words
Estimate from data quantities like: Pr(“Place” in prefix|LOCATION)
If P(“Wean Hall Rm 5409” = LOCATION) is above some threshold, extract it.
A “Naïve Bayes” Sliding Window
Model
[Freitag 1997]
…
00 : pm Place : Wean Hall Rm 5409 Speaker : Sebastian Thrun …
w t-m
w t-1 w t
w t+n
w t+n+1
w t+n+m
prefix
contents
suffix
Create dataset of examples like these:
1.
+(prefix00,…,prefixColon, contentWean,contentHall,….,suffixSpeaker,…)
- (prefixColon,…,prefixWean,contentHall,….,ContentSpeaker,suffixColon,….)
…
Train a NaiveBayes classifier
If Pr(class=+|prefix,contents,suffix) > threshold, predict the content
window is a location.
2.
3.
•
To think about: what if the extracted entities aren’t consistent, eg if the location
overlaps with the speaker?
“Naïve Bayes” Sliding Window
Results
Domain: CMU UseNet Seminar Announcements
GRAND CHALLENGES FOR MACHINE LEARNING
Jaime Carbonell
School of Computer Science
Carnegie Mellon University
3:30 pm
7500 Wean Hall
Machine learning has evolved from obscurity
in the 1970s into a vibrant and popular
discipline in artificial intelligence during
the 1980s and 1990s.
As a result of its
success and growth, machine learning is
evolving into a collection of related
disciplines: inductive concept acquisition,
analytic learning in problem solving (e.g.
analogy, explanation-based learning),
learning theory (e.g. PAC learning), genetic
algorithms, connectionist learning, hybrid
systems, and so on.
Field
Person Name:
Location:
Start Time:
F1
30%
61%
98%
Finite State Transducers
Finite State Transducers for IE


Basic method for extracting relevant
information
IE systems generally use a collection of
specialized FSTs



Company Name detection
Person Name detection
Relationship detection
Finite State Transducers for IE
Frodo Baggins works for Hobbit Factory, Inc.
Text Analyzer:
Frodo
– Proper Name
Baggins – Proper Name
works
– Verb
for
– Prep
Hobbit
– UnknownCap
Factory – NounCap
Inc
– CompAbbr
Finite State Transducers for IE
Frodo Baggins works for Hobbit Factory, Inc.
Some regular expression for finding company names:
“some capitalized words, maybe a comma,
then a company abbreviation indicator”
CompanyName
= (ProperName | SomeCap)+
Comma?
CompAbbr
Finite State Transducers for IE
Frodo Baggins works for Hobbit Factory, Inc.
Company Name Detection FSA
CAB
word
1
(CAP | PN)
2
comma
3
CAB
4
word
(CAP| PN)
CAP = SomeCap, CAB = CompAbbr, PN = ProperName,  = empty string
Finite State Transducers for IE
Frodo Baggins works for Hobbit Factory, Inc.
Company Name Detection FST
CAB  CN
word  word
1
(CAP | PN)  
2
comma  
(CAP| PN)  
3
CAB  CN
4
word  word
CAP = SomeCap, CAB = CompAbbr, PN = ProperName,  = empty string, CN = CompanyName
Finite State Transducers for IE
Frodo Baggins works for Hobbit Factory, Inc.
Company Name Detection FST
CAB  CN
word  word
1
(CAP | PN)  
2
comma  
3
CAB  CN
4
word  word
(CAP| PN)  
Non-deterministic!!!
CAP = SomeCap, CAB = CompAbbr, PN = ProperName,  = empty string, CN = CompanyName
Finite State Transducers for IE



Several FSTs or a more complex FST can be
used to find one type of information (e.g.
company names)
FSTs are often compiled from regular
expressions
Probabilistic (weighted) FSTs
Finite State Transducers for IE
FSTs mean different things to different researchers
in IE.
 Based on lexical items (words)
 Based on statistical language models
 Based on deep syntactic/semantic analysis
Example: FASTUS


Finite State Automaton Text Understanding
System (SRI International)
Cascading FSTs




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Recognize names
Recognize noun groups, verb groups etc
Complex noun/verb groups are constructed
Identify patterns of interest
Identify and merge event structures
Hidden Markov Models
Hidden Markov Models formalism
HMM = probabilistic FSA
HMM = states s1, s2, …
(special start state s1
special end state sn)
token alphabet a1, a2, …
state transition probs P(si|sj)
token emission probs P(ai|sj)
Widely used in many language processing tasks,
e.g., speech recognition [Lee, 1989], POS tagging
[Kupiec, 1992], topic detection [Yamron et al, 1998].
Applying HMMs to IE



Document  generated by a stochastic process
modelled by an HMM
Token  word
State  “reason/explanation” for a given token




‘Background’ state emits tokens like ‘the’, ‘said’, …
‘Money’ state emits tokens like ‘million’, ‘euro’, …
‘Organization’ state emits tokens like ‘university’,
‘company’, …
Extraction: via the Viterbi algorithm, a dynamic
programming technique for efficiently computing the
most likely sequence of states that generated a
document.
HMM for research papers:
transitions [Seymore et al., 99]
HMM for research papers:
emissions [Seymore et al., 99]
ICML 1997...
submission to…
to appear in…
carnegie mellon university…
university of california
dartmouth college
stochastic optimization...
reinforcement learning…
model building mobile robot...
supported in part…
copyright...
author
title
institution
note
Trained on 2 million words of BibTeX data from the Web
...
What is an HMM?



Graphical Model Representation: Variables by time
Circles indicate states
Arrows indicate probabilistic dependencies between states
What is an HMM?



Green circles are hidden states
Dependent only on the previous state: Markov process
“The past is independent of the future given the
present.”
What is an HMM?


Purple nodes are observed states
Dependent only on their corresponding hidden state
HMM Formalism



S
S
S
S
S
K
K
K
K
K
{S, K, P, A, B}
S : {s1…sN } are the values for the hidden states
K : {k1…kM } are the values for the observations
HMM Formalism
S
A
S
B
K




K
A
S
B
K
A
S
A
S
B
K
{S, K, P, A, B}
P = {pi} are the initial state probabilities
A = {aij} are the state transition probabilities
B = {bik} are the observation state probabilities
K
Emission
probabilities
Transition
probabilities

Author
Y
0.1
A
0.1
0.1
C
0.8
Year
0.9
Title
0.5
A
0.6
B
0.3
C
0.1
0.8
dddd
0.8
dd
0.2
Journal
0.2
X
0.4
B
0.2
Z
0.4
Need to provide structure of HMM & vocabulary


0.5
Training the model (Baum-Welch algorithm)
Efficient dynamic programming algorithms exist for


Finding Pr(K)
The highest probability path S that maximizes Pr(K,S) (Viterbi)
Using the HMM to segment


Find highest probability path through the HMM.
Viterbi: quadratic dynamic programming algorithm
115 Grant street Mumbai 400070
115
Grant
………..
400070
House
House
House
Road
Road
Road
City
City
City
Pin
Pint
o
o
Pint
Most Likely Path for a Given Sequence

The probability that the path p 0 ...p N is taken and
the sequence x1...xL
is generated:
L
Pr(x1...xL , p0 ...p N ) = a0 p1  bpi ( xi ) api pi1
i =1
transition
probabilities
emission
probabilities
Example
0.4
0.2
0.5
A
C
G
T
0.4
0.1
0.2
0.3
0.8
A
C
G
T
1
begin
0
0.5
A
C
G
T
0.4
0.1
0.1
0.4
0.6
3
0.2
2
0.8
0.2
0.3
0.3
0.2
A
C
G
T
0.1
0.4
0.4
0.1
end
5
0.9
4
0.1
Pr(AAC, p ) = a01  b1 (A)  a11  b1 (A)  a13  b3 (C)  a35
= 0.5  0.4  0.2  0.4  0.8  0.3  0.6
Finding the most probable path
o1
ot-1
ot
ot+1
oT

Find the state sequence that best explains the observations

Viterbi algorithm (1967)

arg max P ( X | O )
X
Viterbi Algorithm
x1
xt-1
j
o1
ot-1
ot
ot+1
oT
 j (t ) = max P( x1...xt 1 , o1...ot 1 , xt = j , ot )
x1 ...xt 1
The state sequence which maximizes the
probability of seeing the observations to
time t-1, landing in state j, and seeing the
observation at time t
Viterbi Algorithm
x1
xt-1
xt
xt+1
o1
ot-1
ot
ot+1
oT
 j (t ) = max P( x1...xt 1 , o1...ot 1 , xt = j , ot )
x1 ...xt 1
 j (t  1) = max  i (t )aijb jo
t 1
i
 j (t  1) = arg max i (t )aijb jo
i
t 1
Recursive
Computation
Viterbi : Dynamic Programming
 j (t  1) = max  i (t )aijb jo
t 1
i
No 115 Grant street Mumbai 400070
b jot1
115
Grant
 i (t )
House
………..
400070
House
House

(t  1)
j
Road
Road
City
City
City
Pin
Pint
Road
aij
o
o
Pint
Viterbi : Dynamic Programming
 j (t  1) = max  i (t )aijb jo
t 1
i
No 115 Grant street Mumbai 400070
b jot1
115
 i (tHouse
)
Grant
………..
400070
House
House

(t  1)
j
Road
Road
City
City
City
Pin
Pint
Road
aij
o
o
Pint
Viterbi Algorithm
x1
xt-1
xt
xt+1
xT
o1
ot-1
ot
ot+1
oT
Xˆ T = arg max i (T )
i
Xˆ =  ^ (t  1)
t
X t 1
Compute the most
likely state sequence
by working
backwards
Hidden Markov Models Summary



Popular technique to detect and classify a linear
sequence of information in text
Disadvantage is the need for large amounts of
training data
Related Works




System for extraction of gene names and locations from
scientific abstracts (Leek, 1997)
NERC (Biker et al., 1997)
McCallum et al. (1999) extracted document segments that
occur in a fixed or partially fixed order (title, author, journal)
Ray and Craven (2001) – extraction of proteins, locations,
genes and disorders and their relationships
IE Technique Landscape
IE with Symbolic Techniques

Conceptual Dependency Theory



Frame Theory




Minsky, 1975
a frame stores the properties of characteristics of an entity, action or
event
it typically consists of a number of slots to refer to the properties named
by a frame
Berkeley FrameNet project



Shrank, 1972; Shrank, 1975
mainly aimed to extract semantic information about individual events
from sentences at a conceptual level (i.e., the actor and an action)
Baker, 1998; Fillmore and Baker, 2001
online lexical resource for English, based on frame semantics and
supported by corpus evidence
FASTUS (Finite State Automation Text Understanding System)


Hobbs, 1996
using cascade of FSAs in a frame based information extraction approach
IE with Machine Learning Techniques


Training data: documents marked up with ground
truth
In contrast to text classification, local features
crucial. Features of:




Contents
Text just before item
Text just after item
Begin/end boundaries
Good Features for Information Extraction
Creativity and Domain Knowledge Required!
contains-question-mark
begins-with-number Example word features:

identity of word
contains-question-word
begins-with-ordinal

is in all caps
ends-with-question-mark
begins-with-punctuation  ends in “-ski”
first-alpha-is-capitalized
begins-with-question-word is part of a noun phrase
indented

is in a list of city names
begins-with-subject

is under node X in WordNet orindented-1-to-4
blank
Cyc
indented-5-to-10
contains-alphanum

is in bold font
more-than-one-third-space
contains-bracketed
is in hyperlink anchor
only-punctuation

features of past & future
number

last person name was female prev-is-blank
contains-http

next two words are “and
prev-begins-with-ordinal
contains-non-space
Associates”
shorter-than-30
contains-number
contains-pipe
Good Features for Information Extraction
Creativity and Domain Knowledge Required!
Is Capitalized
Is Mixed Caps
Is All Caps
Initial Cap
Contains Digit
All lowercase
Is Initial
Punctuation
Period
Comma
Apostrophe
Dash
Preceded by HTML tag
Character n-gram classifier
says string is a person
name (80% accurate)
In stopword list
(the, of, their, etc)
In honorific list
(Mr, Mrs, Dr, Sen, etc)
In person suffix list
(Jr, Sr, PhD, etc)
In name particle list
(de, la, van, der, etc)
In Census lastname list;
segmented by P(name)
In Census firstname list;
segmented by P(name)
In locations lists
(states, cities, countries)
In company name list
(“J. C. Penny”)
In list of company suffixes
(Inc, & Associates,
Foundation)
Word Features

lists of job titles,

Lists of prefixes

Lists of suffixes

350 informative phrases
HTML/Formatting Features

{begin, end, in} x
{<b>, <i>, <a>, <hN>} x
{lengths 1, 2, 3, 4, or longer}

{begin, end} of line
Landscape of ML Techniques for IE:
Classify Candidates
Abraham Lincoln was born in Kentucky.
Sliding Window
Boundary Models
Abraham Lincoln was born in Kentucky.
Abraham Lincoln was born in Kentucky.
BEGIN
Classifier
Classifier
which class?
which class?
Classifier
Try alternate
window sizes:
which class?
BEGIN
Finite State Machines
Abraham Lincoln was born in Kentucky.
END
BEGIN
END
Wrapper Induction
<b><i>Abraham Lincoln</i></b> was born in Kentucky.
Most likely state sequence?
Learn and apply pattern for a website
<b>
<i>
PersonName
Any of these models can be used to capture words, formatting or both.
IE History
Pre-Web

Mostly news articles



De Jong’s FRUMP [1982]
 Hand-built system to fill Schank-style “scripts” from news wire
Message Understanding Conference (MUC) DARPA [’87-’95],
TIPSTER [’92-’96]
Most early work dominated by hand-built models


E.g. SRI’s FASTUS, hand-built FSMs.
But by 1990’s, some machine learning: Lehnert, Cardie, Grishman and
then HMMs: Elkan [Leek ’97], BBN [Bikel et al ’98]
Web

AAAI ’94 Spring Symposium on “Software Agents”


Tom Mitchell’s WebKB, ‘96


Much discussion of ML applied to Web. Maes, Mitchell, Etzioni.
Build KB’s from the Web.
Wrapper Induction

Initially hand-build, then ML: [Soderland ’96], [Kushmeric ’97],…
Summary
Sliding Window

Abraham Lincoln was born in Kentucky.

Classifier
which class?

Try alternate
window sizes:

Finite State Machines
Abraham Lincoln was born in Kentucky.
Most likely state sequence?
Information Extraction
Sliding Window
From FST(Finite State
Transducer) to HMM
Wrapper Induction


Wrapper toolkits
LR Wrapper
Readings

[1] M. Ion, M. Steve, and K. Craig, "A hierarchical
approach to wrapper induction," in Proceedings
of the third annual conference on Autonomous
Agents. Seattle, Washington, United States: ACM,
1999.
Thank You!
Q&A