Construction of Personalized and Purpose-OrientedThesaurus

Masaharu YOSHIOKA
Makoto HARAGUCHI

Hokkaido Univ.

Background and Objectives
 Background：– Concept structure of electronic dictionary and thesauri• General purpose thesaurus is too general and they do not have finegranularity abstract concepts to represent users’ particular intention• Concept category for representing user’s particular intention is selective andis not directly corresponds to a single common concept category stored ingeneral thesauri
 Objectives– Propose methodology to construct personalized and purpose-orientedthesaurus• Modification of concept structure of electronic dictionary for particular user’s
intention• Evaluation of Construct Personalized and Purpose-Oriented Thesaurus by
Application to Information Retrieval System

Appropriate Concept Category for Particular Users
Intention
Role of keyword in different situation– Use a keyword as a particular concept• A keyword corresponds to a concrete concept category– Use a keyword as a concept category• A keyword corresponds to an abstract concept category– Use a keyword as representative concept of intended category• A keyword corresponds to an abstract concept category• General thesaurus may not have appropriate concept category

Mechanism of
8mm VCR

Video Equipment Home AppliancePurchasing
VCR

8mm Camera
VCR for watchingmovie at home

VCR

8mm VCRDVD
VHS VCR

Refrigerator

Construction of Tentative Concept CategoryConstruction of concept category from relevant documents– Assumption• Tentative concept category should exist more frequently than usual
documents• Alternative keyword for representing this category exists in relevant
documents– Method• Use mutual information content for selecting an abstract concept category• Collect keywords that belongs to selected category to make tentative
concept category– Evaluation measure for selecting an abstract concept category• Appropriate concept category for characterizing relevant documents
might have higher mutual information content with relevant documents

I (T ;W ) = I (W ;T ) = H (W ) − H (W | T )⎡⎤= ∑ ⎢− p(w) log2 p(w) + ∑ p(t ) p(w | t ) log2 p(w | t )⎥L(1)w∈W ⎣t∈T⎦

G ( w) = − p ( w) log 2 p ( w) + ∑ p(t ) p( w | t ) log 2 p( w | t )t∈T= p(r ) p( w | r ){log 2 p( w | r ) − log 2 p( w)}+ p(r ) p( w | r ){log 2 p( w | r ) − log 2 p( w)}≈ p(r ) p( w | r ) log 2p(w | r )
L (2)
p( w)

Example of Tentative Concept Category

Evaluation measure for selecting an appropriate voncept
vategory
G ' ( w) = p ( w | r ) log 2p(w | r )L (3)p ( w)

Construction method– Calculate evaluation measure for each keyword and candidate
abstract concept category– Select concept that has highest evaluation measure for appropriate
oneG'(w) = 1.58 Machine
G'(w) = 2.53

G'(w) = 2.42

Video Equipment
8mm Camera VCR
G'(w) = 1.95

8mm VCR

Query: VCR for movie

Home Appliance
DVD Refrigerator
G'(w) = 0.82

VHS VCR

DVD Rental... movie ..
DVD ...
VCR Rental....movie ...
VHS VCR ....
Document DatabaseIR System based on Personalized and Purpose-OrientedThesaurusEvaluate effectiveness of tentative concept construction
IR system that uses personalized and purpose-oriented thesaurus forquery expansion– Prototype system• Implementation based on Information Retrieval Package （Uchiyama, 2001）: Baselinesystem– BM25-base IR system• Electronic Dictionary– EDR Dictionary– Goi-Taikei- A Japanese Lexicon日本語語彙体系– Test Collection: NTCIR-1 (Japanese)• Document set: Abstract for conference proceedings: 332918 documents• Number of topic:53– Type of data： Title、Description、Narrative、Concept– Relevance judgment：A（Relevant）,B（Partially relevant）,C（Irrelevant）• Type of retrieval:– long（Title+Description+ Narrative+Concept）– short(Description）• Use B relevance judgment and calculate mean-average precision

Prototype SystemConstruction of retrieval index
1. Apply morphological analyzer to extract initialindex keywords (mostly from noun)
2. Check EDR (or Goi-Taikei) Dictionary about
initial keywords and add concept ID list that
corresponds to initial keywords to index



Information retrieval based on adaptive
generalization
1. Extract initial query keywords by usingmorphological analyzer
2. By using relevant document sets (select 5 relevant
documents by automatic feedback), the systemconstruct tentative concept category
3. Add words of constructed category for query
expansion

Initial Query
ビデオの紹介
ビデオは…
Chasen+Baseline system

ビデオ 紹介
ビデオ …
EDR
ビデオ 3c2a83 3c52fb ..
紹介 1faf20 3d04c8 ..

ビデオ 3c2a83
3c52fb … 紹介
1faf20 3d04c8… ビデオ 3c2a83
3c52fb …

Final Index

Example of Constructed Concept Category
Query title: 次世代インターネット(Next Generation Internet)– Original Keyword: 通信する(to communicate)– Generalized concept: 3cf631 23 subcategories and 56 words– Select 3 words from relevant documents
Query title: 次世代インターネット(Next Generation Internet)
Original Keyword: 通信する(to communicate)3cf631 通信する(to communicate)

Tentative Category
通信する(to communicate)
放送する(to transmit a message
to receivers througha wire or radio system)
中継する(to relay messages,
speeches or music froma broad casting station)

0e64a6 衛星中継する(the act of relaying electric
waves by artificial satellite)
0f07c6 交信する(to exchange communication
with some one)
0f021b5 混信する(to get jammed)

3c1208 電話する(to call a person on the telephone)
3c54cd 放送する(to transmit a message to receivers
through a wire ore radio system)
3d1b03 中継する(to relay messages, speeches ormusic from a broad casting station)

Evaluation Result (EDR)
PP-oriented thesaurus results has better performance thanoriginal thesaurus
 PP-oriented thesaurus has poorer performance than baseline
system

Mean Average Precision
System type
PP-oriented Thesaurus
Original Thesaurus
Baseline SystemLong
0.45870.42830.4880Short
0.35870.31310.4097

Expanded Query Size
System type
PP-oriented Thesaurus
Original Thesaurus
Baseline SystemLong
50.89
46.22
209.90

Short8.50
7.44
186.47

Evaluation Result (Goi-Taikei)
Similar to EDR case
 Goi-Taikei has poorer performance than EDR one

Mean Average Precision
System type
PP-oriented Thesaurus
Original Thesaurus
Baseline SystemLong
0.43520.42820.4880Short
0.31060.30870.4097

Expanded Query Size
System type
PP-oriented Thesaurus
Original Thesaurus
Baseline SystemLong
67.08
36.28
209.90

Short
9.53
6.70
186.47

Discussion
Coverage of thesauri– Since these thesauri don’t have good coverage on technical terms,
baseline system that adds all terms in relevant documents works
well– We need a mechanism to expand queries by using words inrelevant documents

EDR dictionary has better performance than Goi-Taikei– Goi-Taikei has approximately 3000 concept categories and EDR
has approximately 50000 concept categories.
– Because of that, Goi-Taikei does not have appropriate abstract
concept categories for particular purpose

ConclusionPropose methodology to construct personalized and purposeoriented thesaurus– Propose methodology to select relevant term list from generalabstract concept category.
– It improve the performance of IR system compared with originalthesaurus.
– However, it is not sufficient for IR performance compared toautomatic relevance feedback query expansion.

Apply this method to different application domain.
– Construct purpose-oriented thesaurus for a category in open
directory.