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TEMPORAL MODELS
FOR MINING, RANKING AND RECOMMENDATION IN
THE WEB
Tu Nguyen
L3S Research Center
Leibniz Universität Hannover
1
Outline
2
Temporal
Dynamics
Web
Web
Archives
Collaborative
Knowledge
Bases
Social
Networks
Through the Lens of Time..
3
tim
e
4
Temporal
Dynamics
Web
Research Questions
5
• RQ1.1: How do the relevant aspects of an entity-centric query change
around the associated event time, specifically just before, during and
after the event time.
• RQ1.2: Given an entity-centric query of semantical or topical ambiguity
at an event time, how should the ranked list of relevant documents be
formed so that the coverage at top-k is maximized?
Research Questions
6
• RQ1.1: How do the relevant aspects of an entity-centric query change
around the associated event time, specifically just before, after and
during the event time.
Motivation
7
Australia Open
Motivation
8
Winners
Nominations
Movies Actors
Location
Athletes
Australia Open
Winners
Schedule
DrawResults
Motivation
9
t
Jan Feb Mar
Querying
time
Motivation
10
Long-term
cumulativeness
vs. Short-term
interest.
Motivation
11
In addition,
different event
times and types
entail different
characteristics
toward long-
term and short-
term interests.
Problem Statment
12
•Problem (Temporal Entity-Aspect Recommendation): Given an event
entity e and hitting time t as input, find the ranked list of entity
aspects that most relevant with regards to e and t.
Approach Overview
13
Approach Overview
14
Sub-Task
Sub-task
15
• Time and Type cascaded classification
• Semantic relation between task labels
• à joint-learning in cascaded manner
• Features
• Seasonality
• Trending
• Auto-correlation
• Prediction Errors
• SpikeM fitting parameters[1]
[1] Matsubara, Yasuko, et al. "Rise and fall patterns of information diffusion: model and implications." Proceedings of the 18th ACM
SIGKDD international conference on Knowledge discovery and data mining. ACM, 2012.
02060100140
observed
202530
trend
0204060
seasonal
−4002040
1990 1995 2000 2005
random
Time
Decomposition of additive time series
Approach Overview
16
Ranking
Task
Multi-criteria Learning
17
• Multiple Ranking Models
• Idea: divide-and-conquer, each feature-set performs better for certain entity
type and at certain event time.
1. Probability the event entity e, at time t, of type C ∈ {Breaking, Anticipated}
2. Probability e is with subject to C is at event time T ∈ {Before, During, After}
3. We use RankSVM to estimate the ranking function f(X, ω) for yˆa
1 2 3
Ranking Features
18
• Salience features
• Mainly extracted from Wikipedia or long duration query logs
• Avg. TF-IDF
• Language Model-based features
• MLE, Entropy: reward most (cumulated) frequent aspects
• Short-term interest features
• Mainly extracted from recent query logs
• Trending velocity
• Temporal click entropy
• Cross correlation (entity vs. aspect)
• Temporal LM
Datasets
19
• AOL query logs
• 03-2006 to 05-2006: 3 months
• Over 30 mil. Queries
• Manual construction:
• 837 entity queries
• 300 event-related queries
• Ground-truth: 70 queries (Breaking: 30, Anticipated: 40)
Methods for Comparison
20
• Random walk with restart (RWR)
• SOTA time-aware query auto-completion:
• Most popular completion[2]
• Recent MPC[2]
• Last N query distribution[2]
• Predicted next N query distribution[2,3]
• SVM-salience: with all salient features[4]
• SVM-timeliness: with all short-term interest features
• SVM-all: with all features
•[2] S. Whiting and J. M. Jose. Recent and robust query auto-completion. In WWW ‘14.
•[3] M. Shokouhi and K. Radinsky. Time-sensitive query auto-completion. In SIGIR ’12.
•[4] Reinanda, Ridho, Edgar Meij, and Maarten de Rijke. Mining, ranking and recommending entity aspects. In SIGIR’15.
Experiments
21
• How do long-term salience and short-term interest features perform at
different time periods of different event types?
• Breaking: Salience model performs well for before, worsen for after
Experiments (2)
22
• How do long-term salience and short-term interest features perform at
different time periods of different event types?
• Anticipated: Timeliness model performs well for before and after, worsen for
during
Experiments (3)
23
• How does the ensemble ranking model perform compared to the single
model approaches?
Research Questions
24
• RQ1.2: Given an entity-centric query of semantical or topical ambiguity
at an event time, how should the ranked list of relevant documents be
formed so that the coverage at top-k is maximized?
Motivation
25
music
spy satellite mission
beer
beer
Search in November 2019
Motivation
26
music
spy satellite mission
beer
beer
Search in November 2019 Search in March 2020
Temporal Search Results Diversification
27
Objective function of the greedy optimization:
• c: subtopic
• S: incremental set of diversified documents
• q: query
• d: target document
- sensitive to time
- should take document
age into account
Motivation
28
Temporal
Dynamics
Collaborative
Knowledge
Bases
Wikipedia as a Global Memory Place
29
Collective memory in Wikipedia
30
•What triggers human remembering of past events?
Motivation
31
• Wikipedia as a source for global memory
• Largest and most up-to-date online encyclopedia
• Its open construction and negotiation in Wikipedia is an important new cultural
and societal phenomenon
• Indicators for identifying real-world events
• View logs as the proxy for collective memory
• Public page view traffics with a (very) long time span
• Not directly reflect how people forget; significant patterns are a good
estimate of public remembering
Research Questions
32
• RQ2.1: How past events are remembered and what triggers human
remembering of these events in Wikipedia?
• RQ2.2: How do we quantify the semantic relatedness between two
entities / events?
Research Questions
33
• RQ2.1: How past events are remembered and what triggers human
remembering of these events in Wikipedia?
• Large-scale analysis over 5500 high-impact events from
11 event categories
Approach
34
• We propose a 3-step approach, for a given event:
1. Heuristically quantify “remembering scores” of past events within the same
category
• Using page views
2. Rank related past events by the computed remembering scores
• Refer to thesis for details
3. Identify features (e.g., time, location, impact) having a high correlation with
remembering
Approach
35
• Remembering score: A linear mixture model of:
• Cross-correlation coefficient (CCF)
• Or sliding inner product
• a measure of similarity of two series as a function
of the displacement of one relative to the other
• Sum of squared prediction error (SSE) or surprise score
• Holt-winters as prediction model
• Skewness (Kurtosis)
• a measure for the degree of peakedness/flatness
in the variable distribution
Studied Features for Triggered Remembering
36
• Temporal similarity
• Time distance between two events (in days, months or years)
• Time distance based on exponential decay functions
• Location similarity
• Map a geographic hierarchy of event locations as follows:
• City à State à Country -> Neighbor countries -> Continent
• Assign 4 scale values: 4 to same city, 3 to state, 2 to country,1 to
continent
• Impact of Events
• Damaged area/properties/cost/fatalities
• Magnitude (for earthquake events)
• Highest winds, lowest pressure (for Atlantic hurricanes)
Study on Atlantic Hurricanes
37
Location and time have a low effect on the category
Study on Aviation Accidents
38
Location and time have a stronger effect on the category
Lessons Learned
39
• We identified some first patterns for event memory triggering for
diverse event types including natural and manmade disasters as well
as accidents and terrorism.
• Our analysis confirmed the influence of high-level features i.e., time
and location, but other (latent) semantic features of events also
influence which event memories are triggered by an event.
• Interpreting systematically factors contribute to event remembering is
hard, even for humans.
Research Questions
40
• RQ2.2: How do we quantify the semantic relatedness between two
entities / events?
Dynamic Entity Relatedness Ranking
41
TaylorLautner
in“Twilight“
[2008-2012]
TaylorLautner
in“Cuckoo“
[2012-]
TaylorLautner
in“RuntheTide“
[2016]
Dynamic Entity Relatedness Ranking
42
• Dynamic Entity Relatedness: between two entities es , ed , where es is the
source entity and ed is the target entity, in a given time t, is a function
(denoted by ft(es , ed)) with the following properties.
• Asymmetric: ft(ei , ej) != ft(ej , ei)
• Non-negativity: f(ei , ej) ≥ 0
• Indiscernibility of identicals: ei = ej → f(ei , ej) = 1 Elon Tesla
• Dynamic Entity Relatedness Ranking: Given a source entity es and time
point t, rank the candidate entities et
d by their semantic relatedness at time
t+1.
• Prediction task
• Use normalized pageview as supervision
Dynamic Entity Relatedness Ranking
43
• A joint “neural” learning model
• Graph-based representation
• Content-based representation
• Time-series representation
• Neural ranking:
• Early-interaction, (late for ts)
• Pair-wise ranking
• Cross-entropy loss
Temporal time-series based similarity
44
• 1-D Convolution layer
• Decay-guided self-attention mechanism
• Dot-product between feature states.
• The context vector is decay-guided
based on time.
• Decay function: Polynomial Curve
with a single decay (hyper)parameter.
Experiment settings
45
• Datasets
Experiment settings
46
• Baselines
• Wikipedia Link-based (WLM)
• DeepWalk (DW)
• Entity2Vec Model (E2V)
• ParaVecs(PV)
• RankSVM + handcrafted features
• Metrics
• Pearson correlation
• Spearman correlation
• Normalized Discounted Cumulative Gain - NDCG
Page views
Human
judgment
Experiment Results
47
48
Temporal
Dynamics
Web
Archives
Motivation
49
Correlation between time series mined from anchor text
(left, ccf = 0.69, τdelay = 2) and Google Trend (right, ccf = 0.68,
τdelay = 9) for query electoral college
Motivation
50
Time series of popular vote (ccf = 0.94, τdelay = 2), border fence
(ccf = 0.40,τdelay = 1) and heath care reform (ccf = 0.44, τdelay =
2) from anchor text and Google Trend from left to right
Motivation
51
Cumulative signals from anchor text tend to well-reflect real-
world event trend patterns with some slight delay.
Motivation
52
In this work, we rely solely on the Web Archive link-graph to
mine important documents.
Research Questions
53
• RQ3: Given a query and the Web Archive, how do we come up with a
top-k ranked list of documents where the coverage of the most
important documents -- topic-wise and time-wise -- are maximized.
Anchor-text based Retrieval Pipeline
54
Motivation
55
• DivRank[*]
• Rich-get-richer phenomenon
• Has a clear optimization explanation
• [*] Mei, Qiaozhu, Jian Guo, and Dragomir Radev. "Divrank: the interplay of prestige and diversity in information
networks." Proceedings of KDD 2010
Illustrated graph PageRank DivRank
Temporal Random Surfer Model
56
• Time-aware Teleportation
• jump to any snapshot with a time preference
• Time-aware Transition probability
• a snapshot at time ti with high time preference
will have higher transition probability.
• a node most propagates its authority to the
nearest peaked time
• propagation scope is restricted to a time
window
Absorbing Random Walk on Temporal Graph
57
• Vertex-Reinforcement Random walk
• within-snapshot: the transition probability in the Markov random walk (to a
state from others) is reinforced by the number of previous visits to that
state
• cross-snapshots: voting mechanism, only one node gets propagated at a
time
Experiment results
58
Diversity by time Diversity by topics
59
Temporal
Dynamics
Social
Network
Research Questions
60
• RQ4: How do temporal models develop and how do we control and
improve the stability of such models at early-stage?
Research Questions
61
• RQ4: How do temporal models develop and how do we control and
improve the stability of such models at early-stage?
• Task 1: Rumor detection in Twitter
Motivation
62
Motivation
63
The Amuay Explosion news and Castro’ Death rumor spread over Twitter[*]
[*] Jin, Fang, et al. "Epidemiological modeling of news and rumors on twitter.” Workshop on Social Network Mining and Analysis 2013.
Motivation
64
The Amuay Explosion news and Castro’s Death rumor spread over Twitter[*]
[*] Jin, Fang, et al. "Epidemiological modeling of news and rumors on twitter.” Workshop on Social Network Mining and Analysis 2013.
How do we handle the case when it is too
early for any propagation patterns to form?
System pipeline
65
• Sometimes Average is the best..
System pipeline
66
• Sometimes Average is the best..
Dynamic Series Time Structure: feature vector representation:
• incoporate the slopes of features between two consecutive intervals[*]
•[*] Ma, Jing, et al. "Detect rumors using time series of social context information on microblogging websites." CIKM 2015
Tweet-level credibility model
67
Tweet-level credibility model
6619.01.20
Experiment Results
68
Research Questions
69
• RQ4: How do temporal models develop and how do we control and
improve the stability of such models at early-stage?
• Task 2: Personalized blood glucose prediction in clinical domain
70
Temporal
Dynamics
Social
Network
Clinical
domain
Research Questions
71
• RQ4: How do temporal models develop and how do we control and
improve the stability of such models at early-stage?
• Task 2: Personalized blood glucose prediction in clinical domain
• Strategy: allowing model to refuse to predict
Motivation
72
Task: predict BG-level in 1 hour
Motivation
73
Sparsity: Measurements taken
periodically and (somewhat) spontaneously.
Motivation – preliminary results
74
Uncertainty in Machine Learning
75
[*] Digrams adopted from https://www.groundai.com/project/aleatoric-and-epistemic-uncertainty-in-machine-learning-a-tutorial-introduction/1
Ensemble Learning..
Bagging or Boosting Prediction variance
Uncertainty in Machine Learning
76
Go Bayesian..
Posterior distribution Weighted average
[*] Digrams adopted from https://www.groundai.com/project/aleatoric-and-epistemic-uncertainty-in-machine-learning-a-tutorial-introduction/1
However, high
computational cost
Uncertainty in Random Forest
77
Tree
Finite#bootstrapreplicatesB
Tree
Tree
variance
estimatesRF
Ensemble Learning
Uncertainty in Random Forest
78
RF
Tree
Finite#bootstrapreplicatesB
Tree
Tree
variance
estimates
MC noise
sampling
noise
Uncertainty in Random Forest
79
• *Wager, Stefan, Trevor Hastie, and Bradley Efron. "Confidence intervals for random forests: The jackknife and the infinitesimal jackknife." JMLR (2014).
RF
Tree
Finite#bootstrapreplicates(B)
Tree
Tree
variance
estimates
MC noise Bias-
corrected*
B = Θ(n)
Experiment results
80
• Sanity filter: carefully-designed heuristic methods (e.g., no long gap prediction,
no malformed input).
• Stability filter: confidence interval based.
Conclusions
81
Temporal
Dynamics
Web
Web
Archives
Collaborative
Knowledge
Bases
Social
Networks
Search
Recommendations
Anchor-text and
Link-based
Analysis &
Temporal Ranking
Entity and Event
Relatedness
Mining and
Recommendation
Enrichment
methods for cold-
start predictions
ESWC’18 - oral
ECIR’14 - oral
SIGIR’15 (short)
WWW’15 Companion
CoNLL’18 - full
JCDL’14 - oral
Socinfo’17 - full
CIKM’17&18
Workshops

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Temporal models for mining, ranking and recommendation in the Web

  • 1. TEMPORAL MODELS FOR MINING, RANKING AND RECOMMENDATION IN THE WEB Tu Nguyen L3S Research Center Leibniz Universität Hannover 1
  • 3. Through the Lens of Time.. 3 tim e
  • 5. Research Questions 5 • RQ1.1: How do the relevant aspects of an entity-centric query change around the associated event time, specifically just before, during and after the event time. • RQ1.2: Given an entity-centric query of semantical or topical ambiguity at an event time, how should the ranked list of relevant documents be formed so that the coverage at top-k is maximized?
  • 6. Research Questions 6 • RQ1.1: How do the relevant aspects of an entity-centric query change around the associated event time, specifically just before, after and during the event time.
  • 11. Motivation 11 In addition, different event times and types entail different characteristics toward long- term and short- term interests.
  • 12. Problem Statment 12 •Problem (Temporal Entity-Aspect Recommendation): Given an event entity e and hitting time t as input, find the ranked list of entity aspects that most relevant with regards to e and t.
  • 15. Sub-task 15 • Time and Type cascaded classification • Semantic relation between task labels • à joint-learning in cascaded manner • Features • Seasonality • Trending • Auto-correlation • Prediction Errors • SpikeM fitting parameters[1] [1] Matsubara, Yasuko, et al. "Rise and fall patterns of information diffusion: model and implications." Proceedings of the 18th ACM SIGKDD international conference on Knowledge discovery and data mining. ACM, 2012. 02060100140 observed 202530 trend 0204060 seasonal −4002040 1990 1995 2000 2005 random Time Decomposition of additive time series
  • 17. Multi-criteria Learning 17 • Multiple Ranking Models • Idea: divide-and-conquer, each feature-set performs better for certain entity type and at certain event time. 1. Probability the event entity e, at time t, of type C ∈ {Breaking, Anticipated} 2. Probability e is with subject to C is at event time T ∈ {Before, During, After} 3. We use RankSVM to estimate the ranking function f(X, ω) for yˆa 1 2 3
  • 18. Ranking Features 18 • Salience features • Mainly extracted from Wikipedia or long duration query logs • Avg. TF-IDF • Language Model-based features • MLE, Entropy: reward most (cumulated) frequent aspects • Short-term interest features • Mainly extracted from recent query logs • Trending velocity • Temporal click entropy • Cross correlation (entity vs. aspect) • Temporal LM
  • 19. Datasets 19 • AOL query logs • 03-2006 to 05-2006: 3 months • Over 30 mil. Queries • Manual construction: • 837 entity queries • 300 event-related queries • Ground-truth: 70 queries (Breaking: 30, Anticipated: 40)
  • 20. Methods for Comparison 20 • Random walk with restart (RWR) • SOTA time-aware query auto-completion: • Most popular completion[2] • Recent MPC[2] • Last N query distribution[2] • Predicted next N query distribution[2,3] • SVM-salience: with all salient features[4] • SVM-timeliness: with all short-term interest features • SVM-all: with all features •[2] S. Whiting and J. M. Jose. Recent and robust query auto-completion. In WWW ‘14. •[3] M. Shokouhi and K. Radinsky. Time-sensitive query auto-completion. In SIGIR ’12. •[4] Reinanda, Ridho, Edgar Meij, and Maarten de Rijke. Mining, ranking and recommending entity aspects. In SIGIR’15.
  • 21. Experiments 21 • How do long-term salience and short-term interest features perform at different time periods of different event types? • Breaking: Salience model performs well for before, worsen for after
  • 22. Experiments (2) 22 • How do long-term salience and short-term interest features perform at different time periods of different event types? • Anticipated: Timeliness model performs well for before and after, worsen for during
  • 23. Experiments (3) 23 • How does the ensemble ranking model perform compared to the single model approaches?
  • 24. Research Questions 24 • RQ1.2: Given an entity-centric query of semantical or topical ambiguity at an event time, how should the ranked list of relevant documents be formed so that the coverage at top-k is maximized?
  • 26. Motivation 26 music spy satellite mission beer beer Search in November 2019 Search in March 2020
  • 27. Temporal Search Results Diversification 27 Objective function of the greedy optimization: • c: subtopic • S: incremental set of diversified documents • q: query • d: target document - sensitive to time - should take document age into account
  • 29. Wikipedia as a Global Memory Place 29
  • 30. Collective memory in Wikipedia 30 •What triggers human remembering of past events?
  • 31. Motivation 31 • Wikipedia as a source for global memory • Largest and most up-to-date online encyclopedia • Its open construction and negotiation in Wikipedia is an important new cultural and societal phenomenon • Indicators for identifying real-world events • View logs as the proxy for collective memory • Public page view traffics with a (very) long time span • Not directly reflect how people forget; significant patterns are a good estimate of public remembering
  • 32. Research Questions 32 • RQ2.1: How past events are remembered and what triggers human remembering of these events in Wikipedia? • RQ2.2: How do we quantify the semantic relatedness between two entities / events?
  • 33. Research Questions 33 • RQ2.1: How past events are remembered and what triggers human remembering of these events in Wikipedia? • Large-scale analysis over 5500 high-impact events from 11 event categories
  • 34. Approach 34 • We propose a 3-step approach, for a given event: 1. Heuristically quantify “remembering scores” of past events within the same category • Using page views 2. Rank related past events by the computed remembering scores • Refer to thesis for details 3. Identify features (e.g., time, location, impact) having a high correlation with remembering
  • 35. Approach 35 • Remembering score: A linear mixture model of: • Cross-correlation coefficient (CCF) • Or sliding inner product • a measure of similarity of two series as a function of the displacement of one relative to the other • Sum of squared prediction error (SSE) or surprise score • Holt-winters as prediction model • Skewness (Kurtosis) • a measure for the degree of peakedness/flatness in the variable distribution
  • 36. Studied Features for Triggered Remembering 36 • Temporal similarity • Time distance between two events (in days, months or years) • Time distance based on exponential decay functions • Location similarity • Map a geographic hierarchy of event locations as follows: • City à State à Country -> Neighbor countries -> Continent • Assign 4 scale values: 4 to same city, 3 to state, 2 to country,1 to continent • Impact of Events • Damaged area/properties/cost/fatalities • Magnitude (for earthquake events) • Highest winds, lowest pressure (for Atlantic hurricanes)
  • 37. Study on Atlantic Hurricanes 37 Location and time have a low effect on the category
  • 38. Study on Aviation Accidents 38 Location and time have a stronger effect on the category
  • 39. Lessons Learned 39 • We identified some first patterns for event memory triggering for diverse event types including natural and manmade disasters as well as accidents and terrorism. • Our analysis confirmed the influence of high-level features i.e., time and location, but other (latent) semantic features of events also influence which event memories are triggered by an event. • Interpreting systematically factors contribute to event remembering is hard, even for humans.
  • 40. Research Questions 40 • RQ2.2: How do we quantify the semantic relatedness between two entities / events?
  • 41. Dynamic Entity Relatedness Ranking 41 TaylorLautner in“Twilight“ [2008-2012] TaylorLautner in“Cuckoo“ [2012-] TaylorLautner in“RuntheTide“ [2016]
  • 42. Dynamic Entity Relatedness Ranking 42 • Dynamic Entity Relatedness: between two entities es , ed , where es is the source entity and ed is the target entity, in a given time t, is a function (denoted by ft(es , ed)) with the following properties. • Asymmetric: ft(ei , ej) != ft(ej , ei) • Non-negativity: f(ei , ej) ≥ 0 • Indiscernibility of identicals: ei = ej → f(ei , ej) = 1 Elon Tesla • Dynamic Entity Relatedness Ranking: Given a source entity es and time point t, rank the candidate entities et d by their semantic relatedness at time t+1. • Prediction task • Use normalized pageview as supervision
  • 43. Dynamic Entity Relatedness Ranking 43 • A joint “neural” learning model • Graph-based representation • Content-based representation • Time-series representation • Neural ranking: • Early-interaction, (late for ts) • Pair-wise ranking • Cross-entropy loss
  • 44. Temporal time-series based similarity 44 • 1-D Convolution layer • Decay-guided self-attention mechanism • Dot-product between feature states. • The context vector is decay-guided based on time. • Decay function: Polynomial Curve with a single decay (hyper)parameter.
  • 46. Experiment settings 46 • Baselines • Wikipedia Link-based (WLM) • DeepWalk (DW) • Entity2Vec Model (E2V) • ParaVecs(PV) • RankSVM + handcrafted features • Metrics • Pearson correlation • Spearman correlation • Normalized Discounted Cumulative Gain - NDCG Page views Human judgment
  • 49. Motivation 49 Correlation between time series mined from anchor text (left, ccf = 0.69, τdelay = 2) and Google Trend (right, ccf = 0.68, τdelay = 9) for query electoral college
  • 50. Motivation 50 Time series of popular vote (ccf = 0.94, τdelay = 2), border fence (ccf = 0.40,τdelay = 1) and heath care reform (ccf = 0.44, τdelay = 2) from anchor text and Google Trend from left to right
  • 51. Motivation 51 Cumulative signals from anchor text tend to well-reflect real- world event trend patterns with some slight delay.
  • 52. Motivation 52 In this work, we rely solely on the Web Archive link-graph to mine important documents.
  • 53. Research Questions 53 • RQ3: Given a query and the Web Archive, how do we come up with a top-k ranked list of documents where the coverage of the most important documents -- topic-wise and time-wise -- are maximized.
  • 55. Motivation 55 • DivRank[*] • Rich-get-richer phenomenon • Has a clear optimization explanation • [*] Mei, Qiaozhu, Jian Guo, and Dragomir Radev. "Divrank: the interplay of prestige and diversity in information networks." Proceedings of KDD 2010 Illustrated graph PageRank DivRank
  • 56. Temporal Random Surfer Model 56 • Time-aware Teleportation • jump to any snapshot with a time preference • Time-aware Transition probability • a snapshot at time ti with high time preference will have higher transition probability. • a node most propagates its authority to the nearest peaked time • propagation scope is restricted to a time window
  • 57. Absorbing Random Walk on Temporal Graph 57 • Vertex-Reinforcement Random walk • within-snapshot: the transition probability in the Markov random walk (to a state from others) is reinforced by the number of previous visits to that state • cross-snapshots: voting mechanism, only one node gets propagated at a time
  • 58. Experiment results 58 Diversity by time Diversity by topics
  • 60. Research Questions 60 • RQ4: How do temporal models develop and how do we control and improve the stability of such models at early-stage?
  • 61. Research Questions 61 • RQ4: How do temporal models develop and how do we control and improve the stability of such models at early-stage? • Task 1: Rumor detection in Twitter
  • 63. Motivation 63 The Amuay Explosion news and Castro’ Death rumor spread over Twitter[*] [*] Jin, Fang, et al. "Epidemiological modeling of news and rumors on twitter.” Workshop on Social Network Mining and Analysis 2013.
  • 64. Motivation 64 The Amuay Explosion news and Castro’s Death rumor spread over Twitter[*] [*] Jin, Fang, et al. "Epidemiological modeling of news and rumors on twitter.” Workshop on Social Network Mining and Analysis 2013. How do we handle the case when it is too early for any propagation patterns to form?
  • 65. System pipeline 65 • Sometimes Average is the best..
  • 66. System pipeline 66 • Sometimes Average is the best.. Dynamic Series Time Structure: feature vector representation: • incoporate the slopes of features between two consecutive intervals[*] •[*] Ma, Jing, et al. "Detect rumors using time series of social context information on microblogging websites." CIKM 2015
  • 67. Tweet-level credibility model 67 Tweet-level credibility model 6619.01.20
  • 69. Research Questions 69 • RQ4: How do temporal models develop and how do we control and improve the stability of such models at early-stage? • Task 2: Personalized blood glucose prediction in clinical domain
  • 71. Research Questions 71 • RQ4: How do temporal models develop and how do we control and improve the stability of such models at early-stage? • Task 2: Personalized blood glucose prediction in clinical domain • Strategy: allowing model to refuse to predict
  • 75. Uncertainty in Machine Learning 75 [*] Digrams adopted from https://www.groundai.com/project/aleatoric-and-epistemic-uncertainty-in-machine-learning-a-tutorial-introduction/1 Ensemble Learning.. Bagging or Boosting Prediction variance
  • 76. Uncertainty in Machine Learning 76 Go Bayesian.. Posterior distribution Weighted average [*] Digrams adopted from https://www.groundai.com/project/aleatoric-and-epistemic-uncertainty-in-machine-learning-a-tutorial-introduction/1 However, high computational cost
  • 77. Uncertainty in Random Forest 77 Tree Finite#bootstrapreplicatesB Tree Tree variance estimatesRF Ensemble Learning
  • 78. Uncertainty in Random Forest 78 RF Tree Finite#bootstrapreplicatesB Tree Tree variance estimates MC noise sampling noise
  • 79. Uncertainty in Random Forest 79 • *Wager, Stefan, Trevor Hastie, and Bradley Efron. "Confidence intervals for random forests: The jackknife and the infinitesimal jackknife." JMLR (2014). RF Tree Finite#bootstrapreplicates(B) Tree Tree variance estimates MC noise Bias- corrected* B = Θ(n)
  • 80. Experiment results 80 • Sanity filter: carefully-designed heuristic methods (e.g., no long gap prediction, no malformed input). • Stability filter: confidence interval based.
  • 81. Conclusions 81 Temporal Dynamics Web Web Archives Collaborative Knowledge Bases Social Networks Search Recommendations Anchor-text and Link-based Analysis & Temporal Ranking Entity and Event Relatedness Mining and Recommendation Enrichment methods for cold- start predictions ESWC’18 - oral ECIR’14 - oral SIGIR’15 (short) WWW’15 Companion CoNLL’18 - full JCDL’14 - oral Socinfo’17 - full CIKM’17&18 Workshops