Francisco Corella and Karen P. Lewison pomcor Use Noflail  Search at noflail April 2009

1. Searching the Web More Effectively With Multiple Simultaneous Queries Francisco Corella and Karen P. Lewison www.pomcor.com Use Noflail Search at noflail.com April 2009

2. Search Engines Are Effective • First result is often what we are looking for • But there are difficult search problems • Example: finding a conference on search, but not on SEO, is hard: • There are many conferences on SEO • “Search” is used with different meanings in many different contexts • “Conference” has several synonyms • “Conference on search” vs. “searching for conferences” • “Search” may be used to label a site-search box Use Noflail Search at noflail.com

3. Semantics May Address Many of These Difficulties • …by allowing for more precision in query specification and content encoding, through: • Context specification: • Information Retrieval vs. Marketing vs. Search & Rescue… • Concept specification: • Concept of conference vs. the many synonyms of the word “conference” • Specification of relationship between two concepts: • “Conference on search” vs. “searching for conferences” • Exclusion of “non-semantic” words from the index • E.g. the word “Search” used as label of a site-search box Use Noflail Search at noflail.com

4. Semantic Technologies Are Promising but Difficult • Semantics require: • Sophisticated content encoding • A different way of indexing the encoded content • A different way of formulating queries about the encoded content Use Noflail Search at noflail.com

5. While Semantic Technologies Mature, It Is Worth Asking: Is it possible to help users with difficult search problems, today, with the current Web, using an existing index and ordinary queries? Use Noflail Search at noflail.com

6. The Answer: YES In Noflail Search (available at noflail.com), we provide substantial help with difficult search problems, using a better user interface with an unmodified backend accessed through a Web API Use Noflail Search at noflail.com

7. An Unusual Architecture 2. Queries / results api.search.live.net (Web API) Noflail Search Flex Platform Flash Player Browser User’s Laptop 1. Flex code noflail.com Use Noflail Search at noflail.com

8. How Can a User Interface Help with a Difficult Search Problem? • What does a user do when confronted with a difficult search problem? • The user may issue several queries and look at the first page of results of each query, e.g.: • “search conference”: nothing • “web search conference”: nothing • “web search meeting”: nothing • “search technology conference”: finds Semantic Technology Conference, not broad enough • “search technology meeting”: nothing Use Noflail Search at noflail.com

9. What does a user do?(Continued) • The user may go back to some of the queries and view one or two more pages of results • Still nothing found in the example • The user may issue more queries or dig deeper into the result sets of some of the previous queries • Finally, the query “web search meeting” yields the Search Engine Meeting in page 4 Use Noflail Search at noflail.com

10. What does a user do?(Continued) • This is a laborious process: • Going back to earlier queries requires retyping them, or using the back arrow to backtrack past intervening pages, or finding the queries in the browser history • We could think of bookmarking queries, but this is cumbersome---more on this below • To put it informally, when we face a tough search problem: WE FLAIL Use Noflail Search at noflail.com

11. Four Ideas for Helping the User • Let the user save queries • Let the user browse multiple result sets at once • Provide cooperative responses to queries that have zero results • Issue multiple queries simultaneously Use Noflail Search at noflail.com

12. 1. Saving Queries • Queries are saved in Flex local storage • Saved queries are shown in a left panel, on the search page itself Use Noflail Search at noflail.com

13. Use Noflail Search at noflail.com

14. 1. Saving Queries (Continued) • Note: Ordinary bookmarks also allow users to save queries (actually, pages of results), but this is cumbersome: • Three clicks to save a bookmark • Bookmarks not visible from search page • Bookmarks of result pages mixed with bookmarks of ordinary Web pages Use Noflail Search at noflail.com

15. Saving Queries(Continued) • Each new query is placed automatically in the left panel, together with possible follow-up queries • Follow-up queries may include: • A respelling of the original query • Related queries • Subqueries (queries with fewer search terms) if there are no related queries Use Noflail Search at noflail.com

16. Saving Queries(Continued) • Queries are inserted into the left panel with checkmarks that cause them to be deleted automatically when the user issues another query • Thus the user can safely ignore the left panel • The user can save a query by removing its checkmark before issuing the next query • The user can build a database of useful queries, reordering them as needed by drag-and-drop Use Noflail Search at noflail.com

17. 2. Browsing Multiple Result Sets • The user can click on any query in the left panel to see its result set in a center panel (there is also a right panel for ads) • The center panel has the usual page menu at the bottom, which lets the user browse the result set Use Noflail Search at noflail.com

18. Use Noflail Search at noflail.com

19. 2. Browsing Multiple Result Sets(Continued) • Noflail Search remembers the last page visited in each result set, and keeps it in memory • Thus the user can switch from one result set to another with one click and zero delay, and resume browsing where he/she left off • This is what we mean by browsing multiple result sets at once • This lets the user do a manual breadth-first search on multiple result sets effortlessly Use Noflail Search at noflail.com

20. 3. Cooperative Responses to Queries with Zero Results • Queries with zero results are infrequent in the Web at large • But they are important, e.g., in site search • What do traditional search engines do when there are no results? Use Noflail Search at noflail.com

21. Use Noflail Search at noflail.com

22. 3. Cooperative Responses (Continued) • If the query-response were a natural language question-answer, this would be called an uncooperative response, or, informally, stonewalling Use Noflail Search at noflail.com

23. 3. Cooperative Responses(Continued) • It is possible to provide instead a cooperative response that gives: • The maximal subqueries (subqueries with the most terms, hence most specific) that have results, as possible follow-up queries • The minimal subqueries (with the fewest terms, hence most general) that do not have results, as so-to-speak reasons for the failure • These subqueries are listed in the left panel, and the user can immediately browse the result sets of all the possible follow-up queries Use Noflail Search at noflail.com

24. Suggested follow-ups Two separate reasons for the failure Use Noflail Search at noflail.com

25. Algorithm for Computing the Cooperative Response • It operates on the graph of subqueries of the original query • Notations: • P=“Paella”, M=“Mussels” , S=“Squid”, E=“Escargots” • “site:myrecipes.com” has been factored out for simplicity Use Noflail Search at noflail.com

26. PMSE PMS PME PSE MSE PM PS PE MS ME SE P M S E Use Noflail Search at noflail.com

27. Algorithm(Continued) • It explores the subgraph of zero-results subqueries • It submits subqueries in parallel to the Web API • It submits a subquery as soon as it knows that all its parents have zero results; hence when a subquery with results is found, it must be maximal • It collects subqueries with zero results, but when a new one is found, it throws away its parents, so that, at the end, the collection contains the minimal subqueries with zero results Use Noflail Search at noflail.com

28. Example • The animation in the next slide illustrates a possible run of the algorithm: • Orange=“Issued, no response yet”; Green=“Has results”; Red=“Zero results”; Red-but-crossed=“Zero results but not minimal” • When multiple subqueries are outstanding, their results may come back in any order; the order in the animation is just an example Use Noflail Search at noflail.com

29. Click to animate PMSE PMS PME PSE MSE PM PS PE MS ME SE P M S E Use Noflail Search at noflail.com

30. Example(Continued) • Results: • Maximal subqueries with results (green) • PM = “Paella Mussels” • PS = “Paella Squid” • MS = “Mussels Squid” • Minimal subqueries with zero results (red, not crossed) • PMS = “Paella Mussels Squid” • E = “Escargots” Use Noflail Search at noflail.com

31. 4. Issuing multiple queries simultaneously • We’ve just used that idea for the previous algorithm! • Cooperative responses would not be practical without the ability to issue queries in parallel against the Web API: • Parallel queries: time linear in number of terms; just a few seconds even when forty or fifty subqueries have to be submitted • Sequential queries: time exponential in number of terms; could take 15 or 20 seconds for a 6-term query that requires submitting 30 or 40 subqueries Use Noflail Search at noflail.com

32. 4. Issuing multiple queries simultaneously (Continued) • Multiple simultaneous queries may also be used to prefetch follow-up queries, even when the original query has results • Recall that follow-up queries may include: • A respelling of the original query • Related queries • Subqueries if there are no related queries • Prefetching would mean zero delay even the first time the user clicks on a follow-up query Use Noflail Search at noflail.com

33. 4. Issuing multiple queries simultaneously (Continued) • But there is a downside: resource consumption at the backend! • Queries with results: • If a query has N follow-up queries in the average, prefetching would take (N+1) more resources • Limited benefit • Queries with zero results: • Big benefit: cooperative responses • Cooperative responses are expensive, but queries with zero results are very rare Use Noflail Search at noflail.com

34. 4. Issuing multiple queries simultaneously (Continued) • After discussion with the Microsoft (the backend provider): • No prefetching of follow-up queries when the original query has results • Simultaneous queries OK to compute cooperative responses when the query has zero results • We only do the zero-results analysis for queries with no more than 6 terms. Use Noflail Search at noflail.com

35. General Boolean Queries (Queries with AND, OR, NOT) • Not implemented yet in Noflail Search • The white paper at http://www.pomcor.com/whitepapers/multisearch.pdfproposes a method for suggesting follow-up queries to Boolean queries, and an algorithm that provides cooperative responses to Boolean queries that produce zero results. • Here we just give an example of a possible run of that algorithm for a particular query Use Noflail Search at noflail.com

36. Illustration of the General Algorithm • Query: PME+PSE, i.e. (Paella AND Mussels AND Escargots) OR (Paella AND Squid AND Escargots) with site constraint factored out as before • Key idea: • The user is only interested in subqueries of PME and PSE; not interested in subqueries with both M and S. • The subquery graph now has an area of interest • Black: subquery of interest • Grey: subquery not of interest Use Noflail Search at noflail.com

37. PMSE PMS PME PSE MSE PM PS PE MS ME SE P M S E Use Noflail Search at noflail.com

38. Illustration of the General Algorithm (Continued) • Since PME+PSE has zero results, both PME and PSE must have zero results Use Noflail Search at noflail.com

39. PMSE PMS PME PSE MSE PM PS PE MS ME SE P M S E Use Noflail Search at noflail.com

40. Illustration of the General Algorithm (Continued) • The algorithm produces: • The maximal subqueries among those of interest that have results • The minimal subqueries among those of interest that have zero results • The animation in the next slide illustrates a possible run of an algorithm Use Noflail Search at noflail.com

41. PMSE PMS PME PSE MSE PM PS PE MS ME SE P M S E Use Noflail Search at noflail.com

42. Illustration of the General Algorithm (Continued) • Results: • Maximal subqueries of interest with results (green) • PM = “Paella AND Mussels” • PS = “Paella AND Squid” • Minimal subqueries of interest with zero results (red, not crossed) • E = “Escargots” Use Noflail Search at noflail.com

43. For More Information • White paper: http://www.pomcor.com/whitepapers/multisearch.pdf • Presentation in PDF format (without animation) available at the Search Engine Meeting Web site: http://www.infonortics.eu/searchengines/index.html • For comments, questions or to get the animated PowerPoint file, send email to Francisco Corella <fcorella@pomcor.com> Use Noflail Search at noflail.com