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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. Search Engines Are Effective. First result is often what we are looking for But there are difficult search problems

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francisco corella and karen p lewison www pomcor com use noflail search at noflail com april 2009

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

search engines are effective
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

semantics may address many of these difficulties
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

semantic technologies are promising but difficult
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

while semantic technologies mature it is worth asking
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

the answer yes
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

an unusual architecture
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

how can a user interface help with a difficult search problem
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

what does a user do continued
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

what does a user do continued10
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

four ideas for helping the user
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

1 saving queries
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

1 saving queries continued
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

saving queries continued
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

saving queries continued16
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

2 browsing multiple result sets
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

2 browsing multiple result sets continued
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

3 cooperative responses to queries with zero results
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

3 cooperative responses continued
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

3 cooperative responses continued23
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

slide24

Suggested follow-ups

Two separate reasons for the failure

Use Noflail Search at noflail.com

algorithm for computing the cooperative response
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

slide26

PMSE

PMS

PME

PSE

MSE

PM

PS

PE

MS

ME

SE

P

M

S

E

Use Noflail Search at noflail.com

algorithm continued
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

example
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

slide29

Click to animate

PMSE

PMS

PME

PSE

MSE

PM

PS

PE

MS

ME

SE

P

M

S

E

Use Noflail Search at noflail.com

example continued
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

4 issuing multiple queries simultaneously
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

4 issuing multiple queries simultaneously continued
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

4 issuing multiple queries simultaneously continued33
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

4 issuing multiple queries simultaneously continued34
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

general boolean queries queries with and or not
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

illustration of the general algorithm
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

slide37

PMSE

PMS

PME

PSE

MSE

PM

PS

PE

MS

ME

SE

P

M

S

E

Use Noflail Search at noflail.com

illustration of the general algorithm continued
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

slide39

PMSE

PMS

PME

PSE

MSE

PM

PS

PE

MS

ME

SE

P

M

S

E

Use Noflail Search at noflail.com

illustration of the general algorithm continued40
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

slide41

PMSE

PMS

PME

PSE

MSE

PM

PS

PE

MS

ME

SE

P

M

S

E

Use Noflail Search at noflail.com

illustration of the general algorithm continued42
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

for more information
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 <[email protected]>

Use Noflail Search at noflail.com

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