1. Using lexical chains for keyword extraction
Presenter : Jian-Ren Chen Authors : Gonenc Ercan, Ilyas Cicekli * 2007.IPM

2. Outlines Motivation Objectives Methodology Experiments Conclusions
Comments

3. Motivation
It is a hard and time consuming task to assign keywords to documents.
The automatic keyphrase extraction algorithms are limited with phrases that appear in the text.

4. Objectives
We present a keyword extraction method such that it uses the features based on lexical chains in the selection of keywords for a text.

5. Methodology first occurrence position frequency
last occurrence position

6. Methodology – Lexical chains
WordNet - synonym、hyponym/hypernym
more than one relationship
up to 3 levels of depth
identify nouns
only consider individual words

7. Methodology – lexical chains
Lexical chain score of a word:
Direct Lexical chain score of a word:
Lexical chain span score of a word:
Direct lexical chain span score of a word:
59 (=7 · )
28 (=4 · 7)

8. Experiments - Datasets
Corpus Name
Texts in corpus
Number of
Training
Documents
Testing
Total
Journal Articles
full texts 55 20 75
Global corpus
abstracts
110 45
155
- extract 1, 5, 10, 15 keywords for each document

9. Experiments Lexical chain score of a word:
Direct Lexical chain score of a word:
Lexical chain span score of a word:
Direct lexical chain span score of a word:

10. Experiments

11. Experiments

12. Conclusions
According to the results that are obtained, the lexical chain features improve the precision significantly in the keyword extraction process.

13. Comments
Advantages
Lexical chains will more consider the semantic relationships
Applications
keyword extraction