Cross-Community Influence in Discussion Fora

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  • 1. Digital Enterprise Research Institute www.deri.ie Cross-Community Influence in Discussion Fora Václav Belák, Samantha Lam, Conor Hayes Stefan.Decker@deri.org http://www.StefanDecker.org/© Copyright 2010 Digital Enterprise Research Institute. All rights reserved.
  • 2. MotivationDigital Enterprise Research Institute www.deri.ie •  Online social communities represent an important cultural and business asset in context of many services on the Web •  Management and exploitation of these communities has thus become important and one way to do it is to focus on influential actors •  Social influence has been intensively studied in SNA, but can we extend the notion of influence to the level of communities? forum A forum B 5 2 1 4 6 3 7
  • 3. Research QuestionsDigital Enterprise Research Institute www.deri.ie •  How can we identify communities persistently affecting other communities? •  Given a specific community, which communities does it influence? Which communities are dependent on the activity of others? •  Over time, how can we identify that a community is being increasingly influenced or even overtaken by another community?
  • 4. Methods: Definition of ImpactDigital Enterprise Research Institute www.deri.ie •  We propose to take two factors into account: 1.  degree of community membership of the users 2.  centrality of the users within each community •  we used in-degree (# replies of a user) •  For general case of n users and k communities define: •  n × k membership matrix M •  n × k centrality matrix C •  Cross-community k × k impact matrix J can then be obtained as a product of the two matrices: ! 1 # 0 $ & ! 2 # 0 $ & M = # 0.2 0.8 &, C = # 10 10 & # 0 1 & # 0 5 & " % " % ! 4 2 $ J = M TC = # & " 8 13 % •  Communities have usually different sizes, we therefore work with normalised impact matrix: J ˆ Ji, j = n i, j ! Ml,i l=1
  • 5. Methods: Impact-based MeasuresDigital Enterprise Research Institute www.deri.ie •  Diagonal elements of J contain independence values (self-impact) ! 4 2 $ J =# & •  Total impact a community has on others is its importance " 8 13 % •  Total impact other communities have on a community is the community’s dependence •  Level of dispersion (heterogeneity) of importance/dependence of community i can be measured as an entropy of a an i-th row/column of the impact matrix •  Is a community broadly influential or does it influence only few other communities?
  • 6. Evaluation Data-SetDigital Enterprise Research Institute www.deri.ie •  10 years of data of the largest Irish discussion board system •  Segmented using 1 week sliding window •  1 week window represents approx. 84% of cross-fora posting activity •  448 snapshots in total •  636 communities, 73k users, 8M posts
  • 7. Clustering Fora By I. and D. Digital Enterprise Research Institute www.deri.ie Aggregate impact matrices from the individual snapshots and cluster the communities (by k-means) embedded in the row and column spaces of the aggregate matrix. ● ● 7 ● 4 2.5 ● ! 1 2 $ 2 ! 133 5 2 $ ● ● ● ● ˆ J1 = # ˆ82 ● &, J = # ● & ● ● ● ● 2.0 ● ● ● ● ● ● ● 3 2 4 6 8 10 " 3 3 % " 3 5 %3 5 7 9 log(dependence)log(importance) ● 1.5 ● ● ˆ ˆ J1 + J 2 ! 3 2 $ 2 ˆ J agg = =# 1.0 & 2 " 3 4 % 1 0.5 0.0 0 0.3 0.4 0.5 0.6 0.7 0.4 0.5 0.6 0.7 0.8 row entropy column entropy
  • 8. Overall I/D over Time Digital Enterprise Research Institute www.deri.ie Take the communities with the highest importance and dependence at each week and plot them over time. Role Playing After Hours Films Games Computers & Tech. Quake Sports After Hours Literature Half−Life Work & Jobs Webgames Humanities Recycle Bin Computers & Tech. Humour Television Reaver Humanities Help Desk Science Feedback Newbies & FAQ Humour Freemasons Moderators Comeonbanus Counter−Strike Lord of the Rings PearTree House History & Heritage Digital Art & Design Help Desk The Illuminati FNWAI Tipp Inst IrelandOffline The Thunderdome HoLL Ask Doctor Demento Lubnip Politics The Cuckoos Nest Events Spell Czechs Soccer Knights of the R.T. PBAN Week 1 Week 25 Week 50 Week 75 Week 100 Week 125 Week 150 Week 175 Week 200 Week 225 Week 250 Week 275 Week 300 Week 325 Week 350 Week 375 Week 400 Week 425Week 1 Week 25 Week 50 Week 75 Week 100 Week 125 Week 150 Week 175 Week 200 Week 225 Week 250 Week 275 Week 300 Week 325 Week 350 Week 375 Week 400 Week 425 Color Key Color Key 0 0.2 0.4 0.6 0.8 0 0.05 0.1 0.15 0.2 0.25 0.3 Value Value
  • 9. Cross-Community Infl. over TimeDigital Enterprise Research Institute www.deri.ie Count cases when community i’s impact on j was higher than j’s independence and plot the pairs with the highest counts. Count From (i) To (j) 29 Moderators Reported Posts 22 FNWAI Poker 17 The Thunderdome After Hours 14 PI Mods Personal Issues
  • 10. Moderation of Pers. IssuesDigital Enterprise Research Institute www.deri.ie 7 PI Mods ● Moderators independence 6 ● ● 5 ● ● 4 ● impact ● ● ● ● ● 3 ● ● 2 ● 1 0 150 200 250 300 350 400 450 week
  • 11. ConclusionDigital Enterprise Research Institute www.deri.ie •  The evaluation demonstrated that the framework •  is able to identify highly influential and dependent communities •  can be used for efficient monitoring of the cross-community activity, perhaps even for early alerts •  can identify which communities to stimulate (e.g. by posting a message) s.t. the stimulus spreads efficiently •  We aim to extend it with content analysis •  E.g. What are the most influential communities with respect to a particular topic? •  We will also investigate empirically-observed topic cascades and modify our models accordingly if needed •  Finally, our goal is to propose a method for measuring significance of cross-community impact •  Belák V., Lam S., Hayes C. Cross-Community Influence in Discussion Fora. ICWSM 2012. •  Belák V., Lam S., Hayes C. Targeting Communities to Maximise Information Diffusion. MSND/WWW 2012.
  • 12. Fold, No, Wait, All In!Digital Enterprise Research Institute www.deri.ie ● FNWAI to Poker Poker to FNWAI Pokers indep. 15 ● ● 10 ● impact ● ● ● ● ● ● ● ● ● ● ● ● ●● 5 ● ● ● ● 0 240 260 280 300 320 340 week