1. Autocomplete as Relevancy
Haystack Search Relevance Conference
April 24, 2019
Rimple Shah
Revanth Malay
David Rhodes

2. 2
LexisNexis
 Business – Information for Lawyers and other Professionals
 Mission: Advance the Rule of Law
 Flagship Products: Lexis Advance, Lexis Risk Solutions, Nexis
 Target Markets: Legal, Risk, Government, Academia, Professional Information
Users
 Customers in 130 countries
 Subsidiary of RELX (NYSE: RELX) since 1994
 Primary Direct Competitors: Dow Jones, Thomson Reuters, Wolters Kluwer,
Bloomberg
 > 10,000 employees worldwide

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Agenda
 Autocomplete as Search Relevance
 Use case
 Customizing Solr for Autocomplete
 Architecture Design
 Evaluating Relevance
 Future Roadmap

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Autocomplete is Search Relevance

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Autocomplete in Lexis Advance

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Who’s Your Data?
 The suggestion is the document
<doc>
<field name="query">obamacare</field>
<field name="display">patient protection and affordable care act</field>
<field name="token_count">1</field>
<field name="id">urn:label:7AC7C01A1EF546C4BCDF334557</field>
<field name="popularity">8464</field>
<field name="source">KRM</field>
<field name="region">United States</field>
</doc>

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Where Do Suggestions Come From?
Users’ Queries LexisNexis legal experts

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Data Preparation

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Solr Suggester
 Built-in Solr Search Component
 Features
 Fast in-memory Finite State Transducer data structure
 Easy to add to an existing Solr index

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• “index + query” approach for complex weights calculation, stop
words removal, or basic context filtrationFunctionality
• Lookups against in-memory FST work incredibly fast
• Performance of a well-tuned Solr Index is sufficient for this use
case
Performance
Should We Use Solr Suggester?

11. 11
Basic Solr Configuration
 Keyword Tokenizer
 Lowercase Filter Factory
 EdgeNGram Filter Factory
 MinGramSize=3
 MaxGramSize=30
Motion to Dismiss
 mot
 moti
 motio
 motion
 motion t
 motion to
 motion to di
 motion to dis
 …
 Whitespace Tokenizer
 Lowercase Filter Factory
 EdgeNGram Filter Factory
 MinGramSize=1
 MaxGramSize=30
Motion to Dismiss
 m t d
 mo to di
 mot dis
 moti dism
 motio dismi
 motion dismis
 dismiss
 Whitespace Tokenizer
 Lowercase Filter Factory
Motion to Dismiss
 motion
 to
 dismiss

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Term Frequency
motion to dis
T.F. = 1.0
motion to dismiss
plaintiff’s motion
motion to dismiss
Solution
Problem
motion to dis

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EDisMax's pf2 Parameter
• Boost suggestions that have user query tokens next to each other.
• Example:
User Query: plaintiff’s rebuttal expert witness
Suggestions:
Doc1 : rebuttal expert witness | Score: 292
Doc2 : rebuttal witness and expert testimony | Score: 253

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Preference for First Word Match
Insert an anchor term as the first token in index and query time.
Example :
User query : motion dismiss KXQHZ motion dismiss
Suggestions:
Documents Index
motion to dismiss with prejudice KXQHZ motion to dismiss with prejudice
dismiss motion with prejudice KXQHZ dismiss motion with prejudice

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Incorrectly Matching On Partial Words
• Query suggestion incorrectly considers complete token as partial word and provides token
suggestions that start with the word.
User Query Documents Index
government is a virgin islands government act v i g a
vi is go ac
vir isl gov act
virg isla gove
virgi islan gover
virgin island govern
…….
government

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Correctly Matching On Partial Words
• Condition 1: When user query has no trailing space
•Insert ‘xwkq’ in the beginning of the last token
User Query Documents Index
government is a
xwkq
virgin islands government act xwkqv xwkqi xwkqg xwkqa
xwkqvi xwkqis xwkqgo xwkqac
xwkqvir xwkqgov xwkqact
xwkqvirg xwkqgove
xwkqvirgi xwkqgover
xwkqvirgin xwkqgovern
…….
xwkqgovernment

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Correctly Matching On Partial Words
• Condition 2: When user query has trailing space
• Rest of the Solr analyzers do the job here
User Query Documents Index
government is a_ virgin islands government act xwkqv xwkqi xwkqg xwkqa
xwkqvi xwkqis xwkqgo xwkqac
xwkqvir xwkqgov xwkqact
xwkqvirg xwkqgove
xwkqvirgi xwkqgover
xwkqvirgin xwkqgovern
…….
xwkqgovernment

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Exact Token Match Before Stemmed & Synonym Match
^8
^6
^6
Standard Tokenizer Factory
+
Lowercase Filter Factory
Standard Tokenizer Factory
+
Lowercase Filter Factory
+
Snowball Porter Filter Factory
+
English Possessive Filter Factory
Standard Tokenizer Factory
+
Lowercase Filter Factory
+
Synonym Graph Filter Factory

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Duplicate and Near Duplicate Suggestions
• Reduce the impression of repetitive suggestion by reduce the suggestion word from the same
root
• User Query: zoning var
• Suggestions:

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Reduce Near Duplicate Suggestions
zone variance
zoning variance
zone variances
variance of zoning

variance_zone

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• About 10-12 % of user queries to web search
engines have spelling errors
Spelling Correction

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Spelling Correction

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Architecture Design

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Architecture Design

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Offline Evaluation

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Offline Evaluation Feedback

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Online Evaluation
• Measure user engagement with
autocomplete suggestions
• Click-rate
• Mean Reciprocal Rank (MRR)
• Minimum Keystroke (MKS)

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Future Roadmap

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Any Questions ?

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Thank You
• Rimple Shah
• rimple.shah@lexisnexis.com
• Revanth Malay
• revanth.malay@lexisnexis.com
• David Rhodes
• david.rhodes@lexisnexis.com
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