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Text Classification Using Stochastic Keyword Generation

Text Classification Using Stochastic Keyword Generation. Cong Li , Ji-Rong Wen and Hang Li Microsoft Research Asia August 22nd, 2003. Outline. Introduction Text Classification Using Stochastic Keyword Generation Experimental Results Conclusion and Future Work. Introduction

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Text Classification Using Stochastic Keyword Generation

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  1. Text Classification Using Stochastic Keyword Generation Cong Li, Ji-Rong Wen and Hang Li Microsoft Research Asia August 22nd, 2003

  2. Outline • Introduction • Text Classification Using Stochastic Keyword Generation • Experimental Results • Conclusion and Future Work • Introduction • Text Classification Using Stochastic Keyword Generation • Experimental Results • Conclusion and Future Work

  3. Introduction • Supervised Text Classification • Question: how to use additional data in training to improve the performance? • New Text Classification Problem • Summaries of texts are available in training, which are more indicative of contents • Note: Summaries are not available in classification • Example: classification at a help desk

  4. Example • Email • When getting emails I get a notice that an email has been received but when I try to view the message it is blank. I have also tried to run the repair program off the install disk but that it did not take care of the problem. • Categories • Empty Outlook Message • Cannot Open Word File • Summary • receive emails; some emails have no subject and message body

  5. Outline • Introduction • Text Classification Using Stochastic Keyword Generation • Experimental Results • Conclusion and Future Work

  6. New Text Classification Problem • Spaces • Users’ emails: space X • Categories: space Y • Engineers’ summaries (for training): space S • Assumption • Summaries are much easier to be classified

  7. Text Classification Using SKG Conventional Text Classification Text Classification Using SKG email: x X When getting emails I get a notice that an email has been received but when I try to view the message it is blank. I have also tried to run the repair program off the install disk but that it did not take care of the problem. email: x X When getting emails I get a notice that an email has been received but when I try to view the message it is blank. I have also tried to run the repair program off the install disk but that it did not take care of the problem. SKG classification probability vector: (x)   (email 0.75, receive 0.68, subject 0.45, body 045, … ) classification category: y Y Empty Outlook Message category: y Y Empty Outlook Message

  8. Stochastic Keyword Generation • Generating Keywords from a Given Text • Stochastic Keyword Generation (SKG) • Generate keywords and their conditional probabilities of occurrence given the text • Example emails 0.75 receive 0.68 subject 0.45 body 0.45       When getting emails I get a notice that an email has been received but when I try to view the message it is blank. I have also tried to run the repair program off the install disk but that it did not take care of the problem. Stochastic Keyword Generation

  9. SKG Model new text x

  10. Model for Each Keyword new text x

  11. Learning Using SKG SKG classification

  12. Outline • Introduction • Text Classification Using Stochastic Keyword Generation • Experimental Results • Conclusion and Future Work

  13. Data in Experiments • Data of the Help Desk of Microsoft • 2517 texts from 52 categories • About 10000 unique words in texts • About 1500 unique words in summaries • Conducted stopword removal, but not stemming • Training/Test Split • 5-fold cross validation

  14. Experimental Settings • Classifiers • Linear SVM (Platt 1998; Dumais et al. 1998) • Perceptron algorithm with margins (PAM) (Li et al. 2002) • Methods • Text classification using SKG • Methods for comparison: • Prior • Texts for training • Summaries for training • (text+summary)s for training • Deterministic keyword generation (DKG)

  15. Experimental Results

  16. SKG versus DKG

  17. Discussion email: x X When getting emails I get a notice that an email has been received but when I try to view the message it is blank. I have also tried to run the repair program off the install disk but that it did not take care of the problem. SKG summary: x X receive emails; some emails have no subject and message body probability vector: (x)   (email 0.75, receive 0.68, subject 0.45, body 045, … ) classification category: y Y Empty Outlook Message

  18. Outline • Introduction • Text Classification Using Stochastic Keyword Generation • Experimental Results • Conclusion and Future Work

  19. Conclusion and Future Work • Conclusion • Text classification using SKG significantly outperforms the methods without using it • Future Work • Theoretical analysis of the problem and the proposed method • Applied in different settings

  20. Thank You

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