The document summarizes techniques for deep query understanding in search systems. It discusses query understanding, which involves understanding a user's information need from their query. This allows for query correction, suggestion, expansion, classification and semantic tagging. Query correction reformulates ill-formed queries. Query suggestion provides similar queries. Query expansion adds synonyms to broaden results. Query classification determines the intent or topic of the query. Semantic tagging identifies entities in the query. The document outlines various models for these techniques, including using contextual information and graph representations of search logs.

1. Techniques for
Deep Query Understanding
“Beware of the man who knows the answer before he understands the
question”
Guided By:
Dr. Dhaval Patel,
Assistant Professor,
Department Of CSE,
IIT Roorkee.
Presented By:
Abhay Prakash,
En. No. – 10211002,
CSI, V Year,
IIT Roorkee.

2. (Source: Google)
Introduction: Query Understanding
 Purpose:
 To understand what exactly the user is searching for – his precise intent
 To correct mistakes and guide user to formulate a precise intended query
Query Refinement
Why only this phrase in Bold?
(Source: Google) Query Suggestion

3. Emerging Variety of Queries
 Natural Language Queries instead of Keyword Represented Queries
 “who is the best classical singer in India” instead of “best classical singer India”
 Use of NL Queries increasing (Makoto et.al in [1])
 Local Search Queries
 “Where can I eat cheesecake right now?”
 Context Dependent Queries (Interactive Question Answering
(Source: Bing – location set as US)

4. Background: How results are generated
Query Understanding
(which index parameters to
be used)
Review: Hotel ABC, Civil Lines:
I ate cheesecake, which was really
awesome. (4/5 star)
High Level Architecture of Search Mechanism (Source: Self Made)
INDEX
(Knowledge Base)
Document Understanding
(What and how to Index)
User Query
Results Ranking
Entities: Hotel ABC, cheesecake
Location: Civil Lines
Quality: 0.8
Time: 8:15 PM
“where can I eat cheesecake
right now?”
Data
(Text documents, User
Reviews, Blogs, Tweets,
Linkedin …)
[Time: 8:15 PM]
Intent: Hotel Search
Search for: cheesecake
Location: Civil lines
Time: 8:20 PM

5. Background: QU & Adv. In Search (Weotta in [3])
1. Basic Search
 Direct text match based retrieval of documents
 Restrict search space using facet values provided by user
 Current day example: Online shopping sites
Mechanism in Basic Search (Source: Self Made)
Example of Facets (Source: Flipkart.com)

6. Background: QU & Adv. In Search (Weotta in [3])
2. Advanced Search
 Ranking of result documents based on:
 TF-IDF to identify more relevant documents
 Website authority and popularity
 Keyword weighting
 Not Considered:
 Context, NLP for semantic understanding
 Location of query, time of query
 Example: Google as was in its early stage

7. Background: QU & Adv. In Search (Weotta in [3])
3. Deep Search
 What difference does it bring?
 Requirements:
 Semantic Understanding of Query
 Knowledge of Context, previous tasks
 User Understanding and Personalization

8. Architecture: Query Understanding Module
Query
Query
Suggestion
Query
Correction
Query
Expansion
Query
Classification
Semantic
Tagging
2. Query Refinement 3. Query Intent Detection
QUERY UNDERSTASNDING MODULE
ANSWER
GENERATION
MODULE
1. Query Suggestion
Result
Components of Query Understanding Module (Source: Self Made)

9. Architecture: Query Understanding Module
Query
i) michael jordan berkley
ii) michael jordan NBA
Query
Suggestion
Query
Correction
Query
Expansion
i) michael jordan berkley: academic
ii) michael l. Jordan Berkley: academic
Query
Classification
Semantic
Tagging
Example of purpose of each Component (Source: Self Made)
michal jrdan
michael jordan
i) michael jordan berkley
ii) michael l. jordan berkley
i) [michael jordan: PersonName]
[berkley: Location]: academic
ii) [michael l. jordan: PersonName]
[berkley: Location]: academic

10. Query Correction
 Reformulates the ill-formed (mistaken) search queries
 ex. Macine learning  Machine Learning
 Refinements:
 Spelling error, Two words Merged together, One word separated
 Phrase segmentation (machine + learning  machine learning)
 Acronym Expansion (CSE  Computer Science & Engineering)
 Refinement may be mutually dependent
 “lectures on machne learn”
 learn is a correct term, but should have been learning
 Hence, different terms need to be addressed simultaneously

11.  Problem Modeled by Jiafeng et.al in [10] as
 Original Query (푥 = 푥1 푥2 . . . 푥푛)  Corrected Query (푦 = 푦1 푦2 . . . 푦푛)
 Get y(complete sequence) which has maximum probability of occurrence, given the
sequence x.
 Simple Technique
 Assume terms independent  take 푦푖 with max Pr 푦푖 푥푖
 Prime Disadvantage:
 Reality deviates a lot from assumption
 Ex. “Lectures on machine learning”
Independent Corrections
Query Correction

12. Query Correction
Using Conventional CRF
 What is CRF?
 Probabilistic graphical model, models conditional distribution
of unobserved state sequences
 Trained on given observation sequence
 Trained for getting Pr 푦 푠푒푞푢푒푛푐푒 푥
 Why use CRF? Conditioned on?
 Sequence of words matters (learning machine?)
 푦푖 conditioned on other 푦푖s as well, along with 푥푖
 Corrections are mutually dependent (e.g. machine learning)
 Disadvantage:
 Will require very large amount of data, 푦푖 candidates’ domain open
Conventional CRF

13.  Restricting space of y for the given x
 conditioned 푦푖 on operation also
 표 = 표1 표2 … 표푛, such that 표푖 required to get 푦푖 from 푥푖
 표푖 is operation like deletion, insertion of characters, etc.
 Learning and Prediction
 Dataset of (푥(1), 푦(1), 표(1)), . . . , (푥(푁), 푦(푁), 표(푁))
 Features
 log Pr(푦푖−1|푦푖 ), where the prob. calculated using corpus
 Whether 푦푖 푖푠 표푏푡푎푖푛푒푑 푓푟표푚 푥푖 푎푓푡푒푟 표푝푒푟푎푡푖표푛 표푖 --{0|1}
Basic CRF-QR Model
Query Correction
Basic CRF-QR Model (Jiafeng et. al in [10])

14.  What is new?
 Handles scenario with more than one refinements
 Machine learm  learn  learning
 Sequence of (sequence of operation)
 표 = 표푖,1, 표푖,2, . . . 표푖,푛 i.e. multiple operations on each word
 Intermediate results: 푧푖 = 푧푖,1푧푖,2 . . . 푧푖,푚−1
Extended CRF-QR
Query Correction
Extended CRF-QR Model (Jiafeng et. al in [10])

15. Query Suggestion
 Purpose:
 Suggest similar queries
 Query auto-completion
 Requirements
 Context consideration [7]
 Identifying Interleaved Tasks [9]
 Personalized suggestion [2]
Suggestions on “iit r..”

16. Context aware Query Suggestion (Huanhuan et.al in [7])
Query Suggestion Mechanism (Source: [7])
Query Suggestion
 Query – mapped  Concept
 Concept Suffix tree from log
 Suggestion time: Transition on tree with each query’s concept
 Suggest top queries of that state

17. Concept Suffix Tree
 Concept Discovery
 Queries clustered using set of clicked URLs
 Feature vector 푞푖 =
푛표푟푚 푤푖푗 푖푓 푒푑푔푒 푒푖푗 푒푥푖푠푡푠
0 표푡ℎ푒푟푤푖푠푒
 Each identified cluster is taken as a Concept
 Concept Suffix Tree
 Vertex: state after transition through a sequence of
concepts (of queries)
 Transition in a session
 C2C3C1: transition Beginning  C1  C3  C2
Click-Through Bipartite
Query Suggestion
Context aware Query Suggestion (Huanhuan et.al in [7])

18. Query Suggestion
Task aware Query Suggestion (Allan et.al in [9])
 Why task identification Important?
 Considering Off-Task query in context adversely affect quality of recommendation
 30% sessions contained multiple tasks (Zhen et.al in [8])
 5% sessions have Interleaved tasks (Zhen et.al in [8])
 Identify similar previous queries as On-Task
 consider only On-Task queries as context
Effect of On-Task and Off-Task
queries

19. Query Suggestion
Task aware Query Suggestion (Allan et.al in [9])
 Measures to evaluate similarity between two queries
 Lexical Score: captures similarity at word level directly. Average of:
 Jaccard Coefficient between trigrams from the two queries: how many common trigrams?
 (1 - Levenshtein Edit Distance), which shows closeness at word level
 Semantic Score: maximum of the following two
 푠푤푖푘푖푝푒푑푖푒푎(푞푖 , 푞푗 ): cosine similarity of vector of tf-idf score of Wikipedia documents w.r.t the
two queries.
 푠푤푖푘푡푖표푛푎푟푦 (푞푖 , 푞푗 ): similar to above on Wiktionary entries
 Final Similarity(풒풊, 풒풋) = 휶 . Lexical Score + (1-휶) . Semantic Score
 If Similarity(푞푖, Reference_q) greater than threshold  푞푖 is On-Task Query

20. Query Suggestion
Personalization in Query Suggestion (Milad et.al in [2])
 On character hit of ‘i’
 “Instagram” more popular for female below 25
 “Imdb” more popular for male in 25-44.
 Candidate queries generated by prior general method
 Personalization by re-ranking candidate queries
 Features for feedback earlier global rank
 Original position
 Original score
 Short History Features
 3-Gram similarity with just previous query
 Avg. 3-gram similarity with all previous queries in the session

21. Query Suggestion
Personalization in Query Suggestion (Source: [2])
 Long History Features
 No. of times candidate query issued in past
 Avg. 3-gram similarity with all previous queries in the past
 Demographic Features
 Candidate query frequency over queries by same age group
 Candidate query likelihood -- same age group
 Candidate query frequency -- same gender group
 Candidate query likelihood -- same gender group
 Candidate query frequency -- same region group
 Candidate query likelihood -- same region group

22. Query Expansion
 Sending more words (should generate similar result) to tackle term-miss
 Ex. “Tutorial lecture on ABC”  “Video Lecture on ABC”
 Expansion Tasks:
 Adding synonyms of words
 Morphological words by stemming
 Naïve Approach
 Exhaustive lookup in thesaurus
 Time taking
 Still miss terms of similar intent (terms even semantically far)

23. Query Expansion
Path Constrained Random Walk (Jianfeng et.al in [11])
 Exploiting search logs for identifying terms having similar end result
 Search log data of <Query, Document> clicks
 Graph Representation
 Node Q: seed query
Nodes Q’: queries in search log
Nodes D: documents
Nodes W: words that occur in queries and documents
 Word nodes are the candidate expansion terms
 Edges have scoring function
 Represents probability of transition from start node
to end node
Search Log as Graph

24. Query Expansion
Path Constrained Random Walk (Jiafeng et.al in [11])
 Probability of using w as an expansion word?
 Product of probabilities in Paths starting at
node Q and ending at w
 Top probable words picked, obtained from
random walk
Search Log as Graph

25. Query Classification
 Classifying given query in a predefined Intent Class
 Ex. michael Jordan berkley: academic
 Precise intent by sequence of nodes from root to leaf
 More challenging than document classification
 Short length
 Keyword representation, makes more ambiguous
 Ex. query “brazil germany”
 Older basic techniques
Example Taxonomy (Source: [6])
 Considering single query  statistical techniques like 2-gram/3-gram inference

26. Query Classification
Context aware Query Classification (Huanhuan et.al in [6])
 Resolving ambiguity using context
 Previous Queries ∈ sports, then “Michael Jordan”  sports (Basketball Player)
 Previous Queries ∈ academic, then “Michael Jordan”  academic (ML professor)
 Use of CRF (because training and prediction on sequence)
 Local Features
 Query Terms: Each 푞푡 supports a target category
 Pseudo Feedback:
 푞푡 with concept 푐푡, submitted to an external web directory
 How many of top M results have 푐푡 concept?
 Implicit Feedback:
 Instead of Top M results – only the clicked documents taken

27. Query Classification
Context aware Query Classification (Huanhuan et.al in [6])
 Contextual Features
 Direct association between adjacent labels
 Number of occurrences of adjacent labels < 푐푡−1, 푐푡 >
 Higher weight  higher probability of transit from 푐푡−1to 푐푡
 Taxonomy-based association between adjacent labels
 Given pair of adjacent labels < 푐푡−1, 푐푡 > at level n
 n-1 features of taxonomy-based association between 푐푡−1, 푐푡 considered
 e.g. Computer/Software related to Computer/Hardware, matching at (n-1)th level 
Computer

28. Semantic Tagging
 Identifies the semantic concepts of a word or phrase
 [michael jordan: PersonName] [berkley: Location]: academic
 Useful only if phrases in documents also tagged
 Shallow Parsing Methods
 Part of Speech Tags: e.g. Clubbing consecutive nouns for Named Entity Recognition
 Disadvantage: Sentence Level Long Segments can’t be identified

29. Semantic Tagging
 Hierarchical Parsing Structures
 Trained a semi-Markov CRF on segments
 Features
 Syntactic Features
Parse tree of sentence
Plot

30. Semantic Tagging
 Semantic Dependency Features
 leverage the information about dependencies among different segments
 Ex. “show me a funny movie starring Johnny and featuring Carribbean Pirates”
 ‘Featuring’ takes arguments – “funny movie” and “Carribbean Pirates”
 long distance semantic dependency between the object “movie” and attribute <Plot>

31. Conclusion & Future Work
 End-to-End Discussion of Query Understanding Module Tasks
 Semantic Understanding of queries for intent detection has lot of scope
 Use of NL (grammatically correct) queries rising
 Understanding at the structure level
 User community detection for its application in Query Suggestion
 Based on search behavior
 Community/Topic specific temporal trending of search query

32. References
[1] Makoto P. Kato, Takehiro Yamamoto, Hiroaki Ohshima and Katsumi Tanaka, "Cognitive
Search Intents Hidden Behind Queries: A User Study on Query Formulations," in WWW
Companion, Seoul, Korea, 2014.
[2] Milad Shokouhi, "Learning to Personalize Query Auto-Completion," in SIGIR, Dublin,
Ireland, 2013.
[3] Weotta, "Deep Search," 10 6 2014. [Online]. Available:
http://streamhacker.com/2014/06/10/deepsearch/. [Accessed 6 8 2014].
[4] W. Bruce Croft, Michael Bendersky, Hang Li and Gu Xu, "Query Understanding and
Representation," SIGIR Forum, vol. 44, no. 2, pp. 48-53, 2010.
[5] Jingjing Liu, Panupong Pasupat, Yining Wang, Scott Cyphers and Jim Glass, "Query
Understanding Enhanced by Hierarchical Parsing Structures," in ASRU, 2013.
[6] Huanhuan Cao, Derek Hao Hu, Dou Shen and Daxin Jiang, "Context-Aware Query
Classification," in SIGIR, Boston, Massachusetts, USA, 2009.

33. References (Continued…)
[7] Huanhuan Cao, Daxin Jiang, Jian Pei, Qi He, Zhen Liao, Enhong Chen, Hang Li,
"Context-Aware Query Suggestion by Mining Click-Through and Session Data," in
KDD, Las Vegas, Nevada, USA, 2008.
[8] Zhen Liao, Yang Song, Li-wei He and Yalou Huang, "Evaluating the Effectiveness of
Search Task Trails," in WWW, Lyon, France, 2012.
[9] Allan, Henry Feild and James, "Task-Aware Query Recommendation," in SIGIR,
Dublin, Ireland, 2013.
[10] Jiafeng Guo, Gu Xu, Hang Li and Xueqi Cheng, "A Unified and Discriminative
Model for Query Refinement,“ in SIGIR, Singapore, 2008.
[11] Jianfeng Gao, Gu Xu and Jinxi Xu, "Query Expansion Using Path-Constrained
Random Walks," in SIGIR, Dublin, Ireland, 2013.