1. Time-dependent Similarity Measure of Queries Using Historical Click- through Data Qiankun Zhao*, Steven C. H. Hoi*, Tie-Yan Liu, et al. Presented by: Tie-Yan Liu * This work was done when Zhao and Hoi were interns at Microsoft Research Asia

2. Outline Background Observations and Motivation Our approach Empirical study Future work

3. Background A dilemma for Web search engines ̵ Very short queries ~2.5 ̵ Inconsistency of term usages The Web is not well-organized Users express queries with their own vocabulary

4. Background (cont’d) Solution: query expansion ̵ Document term based expansion (KDD00, SIGIR05) a query can be expanded with top keywords in the top- k relevant documents ̵ Query term based expansion (WWW02, CIKM04) a query can be expanded with similar queries (queries are similar if they lead to similar pages, pages are similar if they are visited by issuing similar queries) ̵ Click-though data were used for query expansion in many previous work.

5. Background (cont’d) Click-through data ̵ Log data about the interactions between users and Web search engines Typical Click-through data representation

6. (month) Observation 1 Accuracy of query similarity Calculated only from the click- through data in that time interval. Calculated from all the click- through data before that time point

7. Observation 2 Event driven and dynamic character of query similarity the keyword “firework” and related pages are becoming more popular one week before the event and reach the peak on July 4th “firework + injuries" and “firework + picture“ have a little delay in terms of the number of times being issued and visited. “firework + market" and “firework + show" become popular and reach their peaks a few days before July 4th

8. Motivations Exploit the click-through data for semantic similarity of queries by incorporating temporal information To combine explicit content similarity and implicit semantic similarity

9. Our Approach

10. Time-Dependent Concepts Calendar schema and pattern Example ̵ Calendar schema ̵ Calendar pattern ̵ is contained in the pattern

11. Time-Dependent Concepts Click-Through Subgroup Example ̵ Based on the schema, and the pattern,,…,, we can partition the data into 7 groups, which correspond to Sun, Mon, Tue, …, Sat.

12. Similarity Measure For efficiency and simplicity, we measure the query similarity in a certain time slot only based on the click-through data. ̵ Vector representation of queries with respect to clicked documents. ̵ w i is defined by Page Frequency (PF) and Inverted Query Frequency (IQF)

13. Similarity Measure Query similarity measures ̵ Cosine function ̵ Marginalized kernel By introducing query clusters, one can model the query similarity in a more semantic way.

14. Time-Dependent Similarity Measure

15. Empirical Evaluation Dataset ̵ Click-through log of a commercial search engine: June 16, 2005 to July 17,2005 Total size of 22GB Only queries from US ̵ Calendar schema and pattern,,, … Divide the data into 24 subgroups Average subgroup size: 59,400,000 query-page pairs

16. Empirical Examples Kids+toy, map+route Time-dependent daily similarityIncremented daily similarity

17. Empirical Examples weather + forecast, fox + news Time-dependent daily similarityIncremented daily similarity

18. Quality Evaluation Experimental Settings ̵ Partition 32-day dataset into two parts First part for model construction Second part for model evaluation ̵ Accuracy is defined as the percentage of difference between the actual similarity and the model-based prediction ̵ 1000 representative query pairs, similarity larger than 0.3 using the entire dataset Half of them are top queries of the month Half are selected manually related to real world events such as “hurricane”.

19. Experimental Results

20. Here “ distance ” is the time difference between the first test data record and the last model construction data record. For example, when the distance is 1 and the training data size is 10, we summarize all the accuracy values that use the I to 10+i days as training and use the 10+1+i as testing.

21. Experimental Results

22. Conclusion Presented a preliminary study of the dynamic nature of query similarity using click-through data Observed and verified that query similarity are dynamic and event driven with real data Proposed an time-dependent model For our future work, we will investigate an adaptive way to determine the most suitable time granularity for two given queries.

23. Thanks! tyliu@microsoft.com http://research.microsoft.com/users/tyliu