The query-
flow graph:
M
Paolo Boldi
Y
Francesco Bonchi
Y
Carlos Castillo
Y
Debora Donato
model and
Y
Aris Gionis
M
Sebastiano Vigna
M
Università degli studi
applications
di Milano, Italy
Y
Yahoo! Research
Barcelona, Spain

The query-
flow graph:
M
Paolo Boldi
Y
Francesco Bonchi
Y
Carlos Castillo
Y
Debora Donato
model and
Y
Aris Gionis
M
Sebastiano Vigna
M
Università degli studi
applications
di Milano, Italy
Y
Yahoo! Research
Barcelona, Spain

R. Baeza-Yates: “Graphs from search engine queries”. SOFSEM 2007.

Basic concepts
User session
ebay autotrader used fox vw ryanair barcelona places barcelona rent barcelona
Radlinksi & Joachims: “Query chains: learning to rank from implicit feedback”. KDD 2005.

Basic concepts
User session
ebay autotrader used fox vw ryanair barcelona places barcelona rent barcelona
Chain/Mission #1 Chain/Mission #2
Radlinksi & Joachims: “Query chains: learning to rank from implicit feedback”. KDD 2005.

Whence come the chains?
ebay autotrader used fox vw
barcelona places barcelona rent barcelona
soccer barcelona soccer barcelona fc
...
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Whence come the chains?
Query-flow
graph
ebay autotrader used fox vw
barcelona places barcelona rent barcelona
soccer barcelona soccer barcelona fc
...
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Query-flow graph
ebay autotrader used fox vw
barcelona places
barcelona rent
s t
soccer
barcelona soccer
barcelona
... barcelona fc
Query chains
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

The query-flow graph
● Directed graph
● Built from a query log
● Nodes are queries
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Frequencies of query transitions

Frequencies of query transitions

Transitions are non-symmetrical
barclona barcelona 93% of the time
barcelona rent barcelona 7% of the time
And when it happens,
the frequencies are
not correlated

The query-flow graph
● Directed graph
● Built from sessions/chains
● Nodes are queries
● Edges hold information, e.g.:
– Aggregate features from query transitions
– Weights derived from those features
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Statistics on query transitions
barcelona places barcelona rent barcelona
Aggregate Data for (q,q')
multiple
users ● Frequency
●
Relative to other transitions from q
● Bags of terms and character n-grams
● Cosine similarity, Jaccard coefficient, ...
● Average time
● Average position in session
● ...
Radlinksi & Joachims: “Query chains: learning to rank from implicit feedback”. KDD 2005.
R. Jones & K. Klinkner “Beyond session timeout”. CIKM 2008.

Our query-flow graph
● Directed graph
● Built from sessions/chains
● Nodes are queries
● Edges hold information, e.g.:
– Aggregate features from query transitions
– Weights derived from those features
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Weighting schemes
● Interested in weights such as:
– w(q,q') = chain(q,q')
●
-or-
– w(q,q') = freq(q,q') / freq(q)
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Weighting schemes
● Interested in weights such as:
– w(q,q') = chain(q,q')
●
-or-
– w(q,q') = freq(q,q') / freq(q)
● chain(q,q') is the chaining probability
– Pr(q, q' in same chain | q, q' in same session)
● freq(q,q') is the frequency of the transition
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Weighting schemes
● Interested in weights such as:
– w(q,q') = chain(q,q')
●
-or-
– w(q,q') = freq(q,q') / freq(q)
● chain(q,q') is the chaining probability
– Pr(q, q' in same chain | q, q' in same session)
● freq(q,q') is the frequency of the transition
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Estimating chain(q,q')
barcelona places barcelona rent barcelona
Data for (q,q')
● Frequency
● N-grams and terms similarity
● Average delta time
● Average position in session
● Clicks between q and q'
● ...
R. Jones & K. Klinkner “Beyond session timeout”. CIKM 2008.

Estimating chain(q,q')
barcelona places barcelona rent barcelona
Data for (q,q') Training labels
● Frequency ● 5,000 consecutive query pairs
N-grams and terms similarity
+ Manually labelled
● ●
● Average delta time ● 2/3 are same-chain
● Average position in session
● Clicks between q and q'
● ...
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Estimating chain(q,q')
barcelona places barcelona rent barcelona
freq(q,q') = 1:
different-chain if
Data for (q,q') α time
● Frequency -β sim.ngrams.jaccard
● N-grams and terms similarity -γ sim.terms.jaccard + δ > θ
● Average delta time same-chain otherwise
● Average position in session
● Clicks between q and q'
● ... freq(q,q') > 1:
C5.0 rules,
+ Training labels 8 rules in total
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Applications of the query-flow graph
● 1. Session → chains segmentation
● 2. Query recommendation
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Applications of the query-flow graph
● 1. Session → chains segmentation
● 2. Query recommendation
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

There are intertwined chains
pointui forum audi ipswich golfers elbow cox ipswich
(photos: commons.wikimedia.org)

Efficient session breaking
1)1. sort the session
2)2. break into contiguous chains
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Sorting: ATSP formulation
pointui forum audi ipswich golfers elbow cox ipswich
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

ATSP formulation
pointui forum audi ipswich golfers elbow cox ipswich
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

ATSP formulation
pointui forum audi ipswich golfers elbow cox ipswich
Weights given by chain(q,q')
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

ATSP solution
pointui forum audi ipswich golfers elbow cox ipswich
Maximize Π chain(qi,qi+1) s.t. TSP constraints
Greedy algorithm with d-steps lookahead
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

ATSP solution
pointui forum audi ipswich cox ipswich golfers elbow
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Breaking using a threshold
pointui forum audi ipswich cox ipswich golfers elbow
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Breaking using a threshold
pointui forum audi ipswich cox ipswich golfers elbow
Chain #1 Chain #2
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Testing set
● Queries from 1,458 users from UK
– Collected queries over 3 months
– Selected users with >1 query
– Partitioned into chains manually
● 415 (28%) were single-chain
● 3.6 chains per user on average

Evaluation wrt ground truth
● Sorting strategy
– Rand index of omniscient breaking strategy
● Breaking strategy
– Rand index
–
–
– Rand index = pair-wise agreements / ( n )
2
●
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Evaluation of reordering strategy
Strategy Optimal Rand Index
Ours 0.99
Original 0.97
Shuffled 0.92
Average over all users

Evaluation of reordering + breaking
Strategy Rand Index
Ours 0.90
Baseline 0.85
Baseline: 30 min. timeout

Evaluation (cont.)
Better rand index
for the “difficult” chains.
Ours and baseline
score 0.85 and 0.71 if we
exclude the cases where
baseline has score of 1
Ours
Baseline: 30' timeout

Applications of the query-flow graph
● 1. Session → chains segmentation
● 2. Query recommendation
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Graph-based
recommendation strategies
●
We use w(q,q') = freq(q,q') / freq(q)
1. Maximum weight from current query (single-step)
2. Random walk with restart to current query
3. Random walk with restart, gain wrt uniform restart
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Sample recommendations
query “apple”
Max. weight Random walk Random walk gain
t t apple
apple ipod apple apple fruit
apple store apple ipod apple ipod
apple trailers apple store apple belgium
amazon apple trailers eating apple
apple mac google apple.nl
itunes amazon apple monitor
pc world argos apple usa
argos itunes apple jobs
currys pc world apple movie download
t : end of session
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Sample recommendations
query “jeep”
Max. weight Random walk Random walk gain
t t jeep
jeep cherokee jeep jeep trails
jeep grand cherokee jeep cherokee jeep kinderkleding
jeep wrangler jeep grand rover jeep compass
land rover bmw jeep cherokee
landrover jeep wrangler swain and jones jeep
ebay land rover jeep bag
chrisler landrover country living spring show
bmw chrysler buy range rover sport XS
nissan google craviotto snare
t : end of session
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

History-based recommendation
● Random walk
– Restart to all the queries in the user's history
– Do not restart uniformly
●
Restart to more recent queries more frequently

History-based recommendations
(current+1 query of context)
banana → apple → ? beatles → apple → ? apple → ?
banana beatles apple
apple apple apple ipod
usb no apple ipod apple trailers
banana cs scarring apple store
giant chocolate bar srg peppers artwork apple mac
where is the seed in a nut ill get you apple fruit
banana shoe bashles apple usa
fruit banana dundee folk songs apple ipod nano
banana cloths the beatles love album apple.com/ipod
eating bugs place lyrics beatles t
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Conclusions and future work
● Session segmentation
– Simple time-outs OK ... but we can do much better
– Particularly important when dealing with super-sessions
● Recommendation with history
– Often one of the two queries “swallows” the other
– Requires tuning e.g. a better way of combining scores
●
Current work: model transition types
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Transition types
barcelona f.c.
Parallel move
Generalize Specialize
Specialize cheap barcelona hotels
Correct
barcelona hotels
brcelona
barcelona
Generalize luxury barcelona hotels
Specialize
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Types of transition inside a chain
● Error correction
– startford cinema → stratford cinema
● Rephrasing
– wikipedia english → english wikipedia
– robbs celebrities → robbs celebs
Rieh and Xie: “Analysis of multiple query reformulations”. IPM 2006.

Types of transition inside a chain
● Generalization (“zoom out”)
– barcelona hotels → barcelona
● Specialization (“zoom in”)
– barcelona soccer → barcelona camp nou
● Parallel move (“pan”)
– barcelona → rome
Rieh and Xie: “Analysis of multiple query reformulations”. IPM 2006.
Zoom-in, zoom-out, pan, names comes from Y!SAMA

Why model refinement types?
● Improved segmentation
– Some refinement sequences are more frequent than
others
● Improved recommendations
P. Boldi, F. Bonchi, C. Castillo, D. Donato, A. Gionis, S. Vigna: “The Query-Flow Graph”. CIKM 2008.

Q&A