Improving Classification Accuracy Using Automatically Extracted Training Data

1. Improving Classification Accuracy Using Automatically Extracted Training Data Ariel Fuxman A. Kannan, A. Goldberg, R. Agrawal, P. Tsaparas, J. Shafer Search Labs Microsoft Research – Silicon Valley Mountain View, CA

2. Web as a Source of Training Data • For classification tasks, large amounts of training data can significantly improve accuracy • How do we create large training sets? • Conventional methods of using human labelers are expensive and do not scale • Thesis: The Web can be used to automatically create labeled data

3. In this talk • Validate the thesis on a task of practical importance: Retail intent identification in Web Search • Present desirable properties of sources of labeled data • Show how to extract labeled data from the sources

4. Importance of Retail Intent Queries Share of Searches (% of total search queries) Share of Paid Clicks (% of queries leading to paid clicks) Just Behave: A Look at Searcher Behavior -Total U.S. MarketComScore Feb 2009

5. Application of Retail Intent • Provide enhanced user experience around Commerce Search

6. Retail intent identification Definition: A query posed to a search engine has retail intent if most users who type the query have the intent to buy a tangible product Examples :

7. Data Sources for Retail Intent • Sources • Web sites of retailers (e.g., Amazon, Walmart, Buy.com) • Training Data • Queries typed directly on search box of retailers • Extraction from toolbar logs URL in toolbar log

8. Desirable Properties of Web Data Sources • Popularity • Sources should yield large amounts of data • Orthogonality • Sources should provide training data about different regions of the training space • Separation • Sources should provide either positive or negative examples of the target class, but not both

9. Popularity • Sources should yield large amounts of data • For retail intent identification • Web site traffic is a proxy for popularity • More traffic means more queries • Choose Web sites of retailers based on publicly available traffic report (Hitwise)

10. Orthogonality • Sources should provide training data about different regions of the training space • For retail intent identification • Positive examples: top sites from “Departmental Stores” and “Classified Ads” (Amazon and Craigslist) • Negative examples: top site from “Reference” (Wikipedia)

11. Separation • Training examples must unambiguously reflect the intended meaning of most users • Example: there is a book called “World War I”, but the intent of the query is mostly non-commercial • Can be enforced by removing groups of confusable queries from the sources

12. Method to Enforce Separation • Create “groups” of positive queries • Compare the word frequency distribution of each group against the negative class using Jensen-Shannon divergence • Remove groups with low divergence

13. Groups for Retail Intent • Extracting groups from the toolbar log URL in toolbar log

14. Enforcing separation property • JS Divergence of Amazon and Craigslist with respect to Wikipedia See paper for experimental validation

15. Experiments • Setup • Built multiple classifiers using manual and automatically extracted labels in the training sets • Classification method: logistic regression, using unigrams and bigrams as features • Test set: 5K queries randomly sampled from a query log and labeled using Mechanical Turk

16. Automatic vs. Manual Accuracy of extracted labels classifier on par with manual labels classifier

17. Combining Manual and Automatically Extracted Marginally different from using only automatically extracted labels

18. Using Unlabeled Data Performance of the automatic labels classifier is still on par with classifiers that start with manual labels and exploit unlabeled data using self-training

19. Conclusions • By carefully choosing the data sources, we can extract valuable training data • Using large amounts of automatically extracted training data, we can get classifiers that are on par with those trained with manual labels • As future work, we would like to apply this experience to other classification tasks