Speaker: Hanghang Tong Carnegie Mellon University Proximity on Large Graphs: definitions, fast solutions and applications Speaker: Hanghang Tong Carnegie Mellon University 2008-7-31 IBM T.J. Watson

Joint work with IBM Spiros Papadimitriou Philip S. Yu Huiming Qu Christos Faloutsos (CMU) Jia-Yu Pan (Google) Yehuda Koren (AT&T Labs) IBM Spiros Papadimitriou Philip S. Yu Huiming Qu Hani Jamjoom Tina Eliassi-Rad (LLNL) Brian Gallagher (LLNL) Kensuke Oonuma (Sony Corp.) Yasushi Sakurai (NTT Labs)

Graphs are everywhere!

Graph Mining: Big Picture + Graph Level Patterns Laws Generators Smith Alan Adam Adam John Jones Tom Peter + Subgraph Level - Community Beck + Node Level Association Correlation Causality Proximity Jack Amy Not covered parts: generator, sampling, optimal graphs…; anomaly could cross all 3 levels Dan Anna Anna Tom Alice Cell Phone SameTime Lotus Mail We are here!

Proximity on Graph: What? a.k.a Relevance, Closeness, ‘Similarity’…

Proximity on Graphs: Why? Link prediction [Liben-Nowell+], [Tong+] Ranking [Haveliwala], [Chakrabarti+] Email Management [Minkov+] Image caption [Pan+] Neighborhooh Formulation [Sun+] Conn. subgraph [Faloutsos+], [Tong+], [Koren+] Pattern match [Tong+] Collaborative Filtering [Fouss+] Many more… Will return to this later

Prox. is effective to ‘deleted’ and absent edges! Link Prediction density Prox. Hist. for a set of deleted links Prox (ij)+Prox (ji) Prox. is effective to ‘deleted’ and absent edges! density Prox. Hist. for a set of absent links Prox (ij)+Prox (ji) Q: How to predict the existence of the link? A: Proximity! [Liben-Nowell + 2003]

Neighborhood Search on graphs … … … … Conference Author Q: what is most related conference to ICDM? A: Proximity! [Sun+ ICDM2005]

Automatic Image Caption Region Image Test Image Keyword Sea Sun Sky Wave Cat Forest Tiger Grass Q: How to assign keywords to the test image? A: Proximity! [Pan+ 2004]

Center-Piece Subgraph(CePS) Input Output CePS guy CePS Original Graph Q: How to find hub for the black nodes? A: Proximity! [Tong+ KDD 2006]

Q: How to find matching subgraph? A: Proximity![Tong+ KDD 2007 b] Input Query Graph Output Best-Effort Pattern Match Data Graph Matching Subgraph Q: How to find matching subgraph? A: Proximity![Tong+ KDD 2007 b]

Roadmap Basic: RWR Variants Motivation Properties Part I: Definitions Generalizations Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion

Why not shortest path? ‘pizza delivery guy’ problem Some ``bad’’ proximities Why not shortest path? ‘pizza delivery guy’ problem ‘multi-facet’ relationship

Why not max. netflow? No punishment on long paths Some ``bad’’ proximities Why not max. netflow? No punishment on long paths

What is a ``good’’ Proximity? … Multiple Connections Quality of connection Direct & In-directed Conns Length, Degree, Weight…

Random walk with restart 1 4 3 2 5 6 7 9 10 8 11 12

Random walk with restart 1 4 3 2 5 6 7 9 10 8 11 12 0.13 0.10 0.05 0.08 0.04 0.02 0.03 Node 4 Node 1 Node 2 Node 3 Node 5 Node 6 Node 7 Node 8 Node 9 Node 10 Node 11 Node 12 0.13 0.10 0.22 0.05 0.08 0.04 0.03 0.02 Nearby nodes, higher scores Ranking vector More red, more relevant

Why RWR is a good score? j i : adjacency matrix. c: damping factor all paths from i to j with length 1 to j with length 2 to j with length 3 Weighted sum

Roadmap Basic: RWR Variants Motivation Properties Part I: Definitions Generalizations Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion

Variant: escape probability Define Random Walk (RW) on the graph Esc_Prob(CMUIBM) Prob (starting at CMU, reaches IBM before returning to CMU) the remaining graph CMU IBM This measurement, with some small modifications, also meets our requirements. Esc_Prob = Pr (smile before cry)

All are “related to” or “similar to” random walk with restart! Other Variants Other measure by RWs Community Time/Hitting Time [Fouss+] SimRank [Jeh+] Equivalence of Random Walks Electric Networks: EC [Doyle+]; SAEC[Faloutsos+]; CFEC[Koren+] String Systems Katz [Katz], [Huang+], [Scholkopf+] Matrix-Forest-based Alg [Chobotarev+] All are “related to” or “similar to” random walk with restart! All these measurement are very similar or closed related to rwr. By related, I mean that we can actually compute them based on rwr. By similar, I mean we can use similar idea to do the fast computation!

Chaptering different measurements Regularized Un-constrained Quad Opt. RWR Norma lize Katz 4 ssp decides 1 esc_prob Esc_Prob + Sink Hitting Time/ Commute Time relax X out-degree Harmonic Func. Constrained Quad Opt. Effective Conductance “voltage = position” String System Physical Models Mathematic Tools

Roadmap Basic: RWR Variants Motivation Properties Part I: Definitions Generalizations Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion

Property: Monotonicity We want: A: degree preserving! [Koren+ KDD06][Tong+ KDD07a][Tong+ SDM08]

Property: Asymmetry [Tong+ KDD07 a] What is Prox from A to B? What is Prox from B to A? What is Prox between A and B?

Asymmetry in un-directed graphs Hanghang’s # 1 employer is IBM The #1 employee of IBM is ... Hanghang IBM So is love…

Roadmap Basic: RWR Variants Motivation Properties Part I: Definitions Generalizations Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion

Group Proximity [Tong+ KDD07 a] Q: How close are Accountants to SECs? A: Prob (starting at any RED, reaches any GREEN before touching any RED again)

Proximity on Attributed Graphs [Tong+ KDD07 b] What is the proximity from node 7 to 10? If we know that…

A: Augmented graphs [Tong+ KDD07 b]

More on Generalizations Attributed on edges [Chakrabarti+ KDD 06] Proximity w/ Time [Minkov+], [Tong+ SDM 2008], [Tong+ CIKM 2008] Proximity w/ Side Information [Tong+ 2008] …

Summary of Part I Goal: Summarize multiple … relationship Solutions Basic: Random Walk with Restart [Pan+ 2004][Sun+ 2006][Tong+ 2006] Properties: Asymmetry, monotonicity [Koren+ 2006][Tong+ 2007] [Tong+ 2008] Variants: Esc_Prob and many others. [Faloutsos+ 2004] [Koren+ 2006][Tong+ 2007] Generalizations: Group Prox, w/ Attr., w/ Time, w/ Side Information [Charkrabarti+ 2006][Tong+ 2007] [Tong+ 2008]

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion B_Lin: RWR BB_Lin: Skewed BGs FastUpdate: Time-Evolving

Preliminary: Sherman–Morrison Lemma = If: Then:

SM: The block-form Or… A B C D And many other variants… Also known as Woodburg Identity Or…

SM Lemma: Applications RLS (Recursive least square) and almost any algorithm in time series! Leave-one-out cross validation for LSR Kalman filtering Incremental matrix decomposition … … and all the fast sol.s we will introduce!

Computing RWR n x 1 n x n n x 1 1 Adjacency matrix Restart p Starting vector Ranking vector 1 4 3 2 5 6 7 9 10 8 11 12 1 n x 1 n x n n x 1

Q: Given query i, how to solve it? Starting vector Ranking vector Adjacency matrix Ranking vector

OntheFly: Slow on-line response O(mE) 1 4 3 2 5 6 7 9 10 8 11 12 0.13 0.10 0.05 0.08 0.04 0.02 0.03 1 4 3 2 5 6 7 9 10 8 11 12 No pre-computation/ light storage Slow on-line response O(mE)

PreCompute R: [Haveliwala+ 2002] c x Q Q 1 4 3 2 5 6 7 9 10 8 11 10 9 12 0.13 0.10 0.05 0.08 0.04 0.02 0.03 10 9 12 2 1 8 R: 3 11 4 6 5 7 c x Q [Haveliwala+ 2002] Q

PreCompute: Fast on-line response Heavy pre-computation/storage cost 1 4 3 2 5 6 7 9 10 8 11 12 0.13 0.10 0.05 0.08 0.04 0.02 0.03 1 4 3 2 5 6 7 9 10 8 11 12 Fast on-line response Heavy pre-computation/storage cost O(n ) 3 O(n ) 2

Q: How to Balance? On-line Off-line

B_Lin: Basic Idea [Tong+ ICDM 2006] 1 4 3 2 5 6 7 9 10 8 11 12 1 4 3 2 5 6 7 9 10 8 11 12 Find Community 5 6 7 9 10 8 11 12 5 6 7 9 10 8 11 12 1 4 3 2 5 6 7 9 10 8 11 12 0.13 0.10 0.05 0.08 0.04 0.02 0.03 1 4 3 2 1 4 3 2 1 4 3 2 5 6 7 9 10 8 11 12 1 4 3 2 5 6 7 9 10 8 11 12 Combine Fix the remaining

B_Lin: details W ~ ~ + ~ W 1: within community ~ Cross-community

W ~ I – c I – c – U S V W1 B_Lin: details SM Lemma! -1 Easy to be inverted LRA difference SM Lemma!

B_Lin: summary Pre-Computational Stage On-Line Stage Q: A: A few small, instead of ONE BIG, matrices inversions On-Line Stage Q: Efficiently recover one column of Q A: A few, instead of MANY, matrix-vector multiplication Efficiently compute and store Q

Query Time vs. Pre-Compute Time Log Query Time Quality: 90%+ On-line: Up to 150x speedup Pre-computation: Two orders saving Log Pre-compute Time

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion B_Lin: RWR BB_Lin: Skewed BGs FastUpdate: Time-Evolving

RWR on Bipartite Graph Observation: n >> m! Examples: authors Author-Conf. Matrix Observation: n >> m! Examples: 1. DBLP: 400k aus, 3.5k confs 2. NetFlix: 2.7M usrs,18k mvs n Conferences m

RWR on Skewed bipartite graphs Q: Given query i, how to solve it? m confs … . . . … . … .. Ar ? ? . … … . .. … . . Ac n aus n m

BB_Lin: Pre-Computation [Tong+ ICDM 06] 2-step RWR for Conferences M = Ac Ar X Step 1: Step 2: Cost: Examples NetFlix: 1.5hr for pre-computation; DBLP: 1 few minutes m conferences All Conf-Conf Prox. Scores n authors

BB_Lin: Pre-Computation [Tong+ ICDM 06] 2-step RWR for Conferences M = Ac Ar X Step 1: Step 2: m conferences All Conf-Conf Prox. Scores n authors

BB_Lin: Pre-Computation [Tong+ ICDM 06] 2-step RWR for Conferences M = Ac Ar X Step 1: Step 2: Cost: Examples NetFlix: 1.5hr for pre-computation; DBLP: 1 few minutes All Conf-Conf Prox. Scores m x m Ac/Ar E edges

BB_Lin: On-Line Stage Read out ! (Base) Case 1: - Conf - Conf authors Ac/Ar E edges Conferences (Base) Case 1: - Conf - Conf Read out !

BB_Lin: On-Line Stage 1 matrix-vec! Case 2: - Au - Conf authors Ac/Ar E edges Conferences Case 2: - Au - Conf 1 matrix-vec!

BB_Lin: On-Line Stage 2 matrix-vec! Case 3: - Au - Au authors Ac/Ar E edges Conferences Case 3: - Au - Au 2 matrix-vec!

BB_Lin: Examples Dataset Off-Line Cost On-Line Cost DBLP a few minutes frac. of sec. NetFlix 1.5 hours <0.01 sec. 400k authors x 3.5k conf.s 2.7m user x 18k movies

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion B_Lin: RWR BB_Lin: Skewed BGs FastUpdate: Time-Evolving

Challenges BB_Lin is good for skewed bipartite graphs for NetFlix (2.7M nodes and 100M edges) On-line cost for query: fraction of seconds w/ 1.5 hr pre-computation for m x m core matrix But…what if the graph is evolving over time New edges/nodes arrive; edge weights increase… On-line cost: 1.5hr itself becomes a part of this!

Q: How to update the core matrix? ~ ?

~ ~ ~ Update the core matrix = = = Step 1: Step 2: X X + X + Ar M M Ac Rank 2 update ~ ~ Model – descriptive for static. Generative, why? = + X

~ Update : General Case = Observation E’ edges changed n authors E’ edges changed Involves n’ authors, m’ confs. Observation ~ M = Ac Ar X m Conferences

Update : General Case Observation: Our Algorithm 64 n authors Observation: the rank of update is small! Real Example (DBLP Post) 1258 time steps E’ up to ~20,000! min(n’,m’) <=132 Our Algorithm m Conferences

Fast-Single-Update log(Time) (Seconds) 176x speedup 40x speedup Our method Our method Datasets

Fast-Batch-Update 15x speed-up on average! Time (Seconds) Our method Our method DBLP post time: 1,258 time steps, 1~18,000 edges changed at each time step 1~132 for rank of update! E’ Min (n’, m’) 15x speed-up on average!

More on “Fast Solutions” FastAllDAP Simultaneously solve multiple linear systems [Tong+ KDD 2007 a] MT3 Multiple-Resolution Analysis on Time [Tong+ CIKM 2008] Fast-ProSIN On-Line response for users’ feedback [Tong+ 2008]

Summary of Part II Goal: Efficiently Solve Linear System(s) Sols. B_Lin: one large linear system [Tong+ ICDM06] BB_Lin: the intrinsic complexity is small [Tong+ ICDM06] FastUpdate: dynamic linear system [Tong+ SDM08] FastAllDAP: multiple linear systems [Tong+ KDD07 a] MT3: [Tong+ CIKM 2008] Fast-ProSIN: [Tong+ 2008]

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion Link Prediction & + Ranking Related Tasks User Specific Patterns Time Related Tasks

Prox. is effective to ‘deleted’ and absent edges! density Link Prediction: existence Prox. Hist. for a set of deleted links Prox (ij)+Prox (ji) Prox. is effective to ‘deleted’ and absent edges! density Prox. Hist. for a set of absent links Prox (ij)+Prox (ji) Q: How to predict the existence of the link? A: Proximity! [Liben-Nowell + 2003]

Link Prediction: direction [Tong+ KDD 07 a] Q: Given the existence of the link, what is the direction of the link? A: Compare prox(ij) and prox(ji) >70% density Prox (ij) - Prox (ji)

Beyond Link Prediction Collaborative Filtering [Fouss+] Name Disambiguation [Minkov+ SIGIR 06] Anomaly Nodes/Edges ‘a’ is abnormal if the neighborhood of ‘a’ is so different [Sun+ ICDM 2005] Here (link prediction, disambiguation, anomaly detection), we want to user proximity to directly quantify/study the relationship between nodes on graphs

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion Link Prediction & + Ranking Related Tasks User Specific Patterns Time Related Tasks

Neighborhood Search on graphs … … … … Conference Author Q: what is most related conference to ICDM? A: Proximity! [Sun+ ICDM2005]

NF: example

gCaP: Automatic Image Caption Q { } Cat Forest Grass Tiger … { Sea Sun Sky Wave } ? {?, ?, ?,} A: Proximity! [Pan+ KDD2004]

Region Image Keyword Test Image Sea Sun Sky Wave Cat Forest Tiger Grass Test Image Keyword

Region Image Keyword Test Image {Grass, Forest, Cat, Tiger} Sea Sun Sky Wave Cat Forest Tiger Grass Keyword

C-DEM: Multi-Modal Query System for Drosophila Embryo Databases [Fan+ VLDB 2008] C-DEM is Isomophic to gCap.

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion Link Prediction & + Ranking Related Tasks User Specific Patterns Time Related Tasks

Center-Piece Subgraph(CePS) Input Output CePS guy CePS Original Graph Q: How to find hub for the black nodes? A: Proximity! [Tong+ KDD 2006] Red: Max (Prox(A, Red) x Prox(B, Red) x Prox(C, Red))

CePS: Example

K_SoftAnd: Relaxation of AND Disconnected Communities Noise Another reason to motivate the k_softand query is that, in some situations, asking an and_query might be too restrictive, especially when the # of the queries is large, or there exist noise in the query set, like in the left figure; or the queries belongs to different remote/dis-connected communities, like in the right figure In both examples, the algorithm will output no answer for AND query Asking AND query?  No Answer!

CePS: 2 SoftAND DB Stat.

Q: How to find matching subgraph? A: Proximity![Tong+ KDD 2007 b] Input Query Graph Output Best-Effort Pattern Match Data Graph Matching Subgraph Q: How to find matching subgraph? A: Proximity![Tong+ KDD 2007 b]

G-Ray: How to? Goodness = Prox (12, 4) x Prox (4, 12) x matching node matching node matching node matching node Goodness = Prox (12, 4) x Prox (4, 12) x Prox (7, 4) x Prox (4, 7) x Prox (11, 7) x Prox (7, 11) x Prox (12, 11) x Prox (11, 12)

Effectiveness: star-query Here is a star-query, we want to a star-shape group of co-authors, with one author coming from each of PODS, IAT and ISBMS. We see Dr. Phillips Yu is in the center and the rest matching authors being well known domain experts in each conf. Query Result

Effectiveness: line-query And here is a line query, we want to find authors from 4 different conferences who cooperate in a line fashion. Result

Effectiveness: loop-query And this is a loop query. Result

Roadmap Motivation Part I: Definitions Part II: Fast Solutions Part III: Applications Conclusion Link Prediction & + Ranking Related Tasks User Specific Patterns Time Related Tasks

Challenge Graphs are evolving over time! New nodes/edges show up; Existing nodes/edges die out; Edge weights change… Q: How to Generalize everything? A: Track Proximity! [Tong+ SDM 2008] However, many real graphs, How can we apply trend analysis tools, e.g. google trend to the graph level?

pTrack/cTrack: Trend analysis on graph level T. Sejnowski Rank of Influential-ness G.Hinton C. Koch Let me give you an example Arrow direction M. Jordan Year

pTrack: Philip S. Yu’s Top-5 conferences up to each year ICDE ICDCS SIGMETRICS PDIS VLDB CIKM ICMCS KDD SIGMOD ICDM SDM 1992 1997 2002 2007 DBLP: (Au. x Conf.) - 400k aus, - 3.5k confs - 20 yrs Databases Performance Distributed Sys. Databases Data Mining

KDD’s Rank wrt. VLDB over years Prox. Rank Data Mining and Databases are more and more relavant! Year

cTrack:10 most influential authors in NIPS community up to each year T. Sejnowski M. Jordan Author-paper bipartite graph from NIPS 1987-1999. 3k. 1740 papers, 2037 authors, spreading over 13 years

T3: Understand Time in Complex Context [Tong+ CIKM 2008] Event Entity t1 e1 b1, b2 e2 b2, b3 t2 e3 e4 b3, b4 t3 e5 b4, b5 t4 e6 b5, b6 e7 b6, b7 t5 e8 t6 e9 b7, b8 Time Cluster, rep. entities: b7,b6, b8 Abnormal Time rep. entities: b5,b4 Time Cluster rep. entities: b3, b2, b1 Output Input

T3: Time-to-Time Proximity Matrix Event Entity t1 e1 b1, b2 e2 b2, b3 t2 e3 e4 b3, b4 t3 e5 b4, b5 t4 e6 b5, b6 e7 b6, b7 t5 e8 t6 e9 b7, b8

More Applications … Clustering Email management [Minkov+ CEAS 06]. Proximity as input [Ding+ KDD 2007] Email management [Minkov+ CEAS 06]. Business Process Management [Qu+ 2008] ProSIN Listen to clients’ comments [Tong+ 2008] TANGENT Broaden Users’ Horizon [Oonuma & Tong + 2008] Ghost Edge Within Network Classification [Gallagher & Tong+ KDD08 b] …

LP: [Liben-Nowell+][Tong+ 2007] Applications Computations Use Proximity as Building block gCap: pTrack/cTrack: LP: [Liben-Nowell+][Tong+ 2007] NF: CePS: G-Ray: T3: GhostEdge: [Gallagher & Tong+ 2008] [Tong+ 2007] [Tong+ 2006] [Pan+ 2004] [Pan+ 2005] [Tong+ 2008] Efficiently Solve Linear System(s) MT3: [Tong+ 2008] Fast-ProSIN: [Tong+ 2008] FastUpdate: [Tong+ 2008] FastAllDAP: [Tong+ 2007] BB_Lin: [Tong+ 2006] B_Lin: [Tong+ 2006] Weighted Multiple Relationship Proximity On Graphs Definitions RWR: [Pan+ 2004][Sun+ 2006][Tong+ 2006] Properties.: [Koren+ 2006]]Tong+ 2007, 2008] Variants: [Faloutsos+ 2004] [Koren+ 2006][Tong+ 2007] Generalizations: [Charkrabarti+ 2006][Tong+ 2007, 2008]

Take-home messages Proximity Definitions Computations Applications RWR and a lot of variants Computations Find out “smoothness” SM Lemma Applications Proximity as a building block

References L. Page, S. Brin, R. Motwani, & T. Winograd. (1998), The PageRank Citation Ranking: Bringing Order to the Web, Technical report, Stanford Library. T.H. Haveliwala. (2002) Topic-Sensitive PageRank. In WWW, 517-526, 2002 J.Y. Pan, H.J. Yang, C. Faloutsos & P. Duygulu. (2004) Automatic multimedia cross-modal correlation discovery. In KDD, 653-658, 2004. C. Faloutsos, K. S. McCurley & A. Tomkins. (2002) Fast discovery of connection subgraphs. In KDD, 118-127, 2004. J. Sun, H. Qu, D. Chakrabarti & C. Faloutsos. (2005) Neighborhood Formation and Anomaly Detection in Bipartite Graphs. In ICDM, 418-425, 2005. W. Cohen. (2007) Graph Walks and Graphical Models. Draft.

References P. Doyle & J. Snell. (1984) Random walks and electric networks, volume 22. Mathematical Association America, New York. Y. Koren, S. C. North, and C. Volinsky. (2006) Measuring and extracting proximity in networks. In KDD, 245–255, 2006. A. Agarwal, S. Chakrabarti & S. Aggarwal. (2006) Learning to rank networked entities. In KDD, 14-23, 2006. S. Chakrabarti. (2007) Dynamic personalized pagerank in entity-relation graphs. In WWW, 571-580, 2007. F. Fouss, A. Pirotte, J.-M. Renders, & M. Saerens. (2007) Random-Walk Computation of Similarities between Nodes of a Graph with Application to Collaborative Recommendation. IEEE Trans. Knowl. Data Eng. 19(3), 355-369 2007.

References H. Tong & C. Faloutsos. (2006) Center-piece subgraphs: problem definition and fast solutions. In KDD, 404-413, 2006. H. Tong, C. Faloutsos, & J.Y. Pan. (2006) Fast Random Walk with Restart and Its Applications. In ICDM, 613-622, 2006. H. Tong, Y. Koren, & C. Faloutsos. (2007) Fast direction-aware proximity for graph mining. In KDD, 747-756, 2007. H. Tong, B. Gallagher, C. Faloutsos, & T. Eliassi-Rad. (2007) Fast best-effort pattern matching in large attributed graphs. In KDD, 737-746, 2007. H. Tong, S. Papadimitriou, P.S. Yu & C. Faloutsos. (2008) Proximity Tracking on Time-Evolving Bipartite Graphs. to appear in SDM 2008.

References B. Gallagher, H. Tong, T. Eliassi-Rad, C. Faloutsos. Using Ghost Edges for Classification in Sparsely Labeled Networks. KDD 2008 H. Tong, Y. Sakurai, T. Eliassi-Rad, and C. Faloutsos. Fast Mining of Complex Time-Stamped Events CIKM 08 H. Tong, H. Qu, and H. Jamjoom. Measuring Proximity on Graphs with Side Information. Submitted. K. Oonuma, H. Tong, and C. Faloutsos. TANGENT: A Novel, “Surprise-me”, Recommendation Algorithm. Submitted.

Thank you! htong@cs.cmu.edu www.cs.cmu.edu/~htong