香港浸会大学：Social Knowledge Dynamics：A Case Study on Modeling Wikipedia

The 10th HKBU-CSD Postgraduate Research Symposium Social Knowledge Dynamics A Case Study on Modeling Wikipedia Presenter: Benyun Shi Supervisor: Prof Jiming liu Department of computer Science Hong Kong Baptist University tember. 200

Social Knowledge Dynamics: A Case Study on Modeling Wikipedia Presenter: Benyun Shi The 10th HKBU-CSD Postgraduate Research Symposium Supervisor: Prof. Jiming Liu Department of Computer Science Hong Kong Baptist University September, 2009

Outline 3 Wikipedia and Social Knowledge Dynamics Previous Work on Wikipedia Degree distribution Reciprocity and feedback loops Motifs 3 Modeling wikipedia's Growth a model about reference a model about degree distribution ◇AOC- based models ☆ Conclusion

2 Outline ❖ Wikipedia and Social Knowledge Dynamics ❖ Previous Work on Wikipedia – Degree distribution – Reciprocity and feedback loops – Motifs ❖ Modeling Wikipedia’s Growth – A model about reference – A model about degree distribution ❖ AOC-based Models ❖ Conclusion

Wikipedia 看祖 anyone can create, edit, as well as delete Some properties v Each article can be treated as a collective"knowledge"of a group of users; Users can exchange"knowledge"through"talk" page; V Users with similar "knowledge may form communities v The underlying structure of some article may inversely influence users knowled 8 Try Beta 3 Benyunsh my tak my preferences my watchlist my contributione a「 edit this page history「 unlatch Hong Kong Baptist University WIKIPEDIA Hong Kong Ba中时Cm香命大)B四包的 Tbe Fre Enoclopee f higher learning in Hong Kong. Formerly known as Hong Kong Baptist College, it became Hong Kong Baptist University in 1994 during the 香港没會大学(没大) presidency of Dr. Daniel C W. TSE, LLD, GBS, CBE, JP, who succeeded the Founding President, Dr Lam Chi-fung. as the second president of HKBU Emblem Motto 篤估力行 u Featured content Upon the retirement of Dr. Tse in 2001 after 30 years of educational and social services to the University and Hong Kong, Prof Ng Ching-fai GBS was appointed as the third president of the University. The chairman of the University Council and Court is Mr WONG Ying-wai, Wilfred Established: 1956 u Rrent events Random article HKBU has four main campuses: Ho Sin Hang Campus(1966), Shaw Campus(1995, Baptist Unvversay Road Campus (1998)and the"Kai Tak

3 Wikipedia • Anyone can create, edit, as well as delete; • Some properties: ✓ Each article can be treated as a collective “knowledge” of a group of users; ✓ Users can exchange “knowledge” through “talk” page; ✓ Users with similar “knowledge” may form communities; ✓ The underlying structure of some article may inversely influence users “knowledge”;

Social Knowledge dynamics Knowledge is embodied in people gathered in communities and networks The road to knowledge is via people, conversations, connections and relationships. Knowledge surfaces through dialog, all knowledge is socially mediated and access to knowledge is by connecting to people that know or know who to contact Denham Grey Social dynamics A society of individuals to react to inner and or outer change Global patterns can emerge from even simple individuals phase transitions, catastrophe, etc Social knowledge dynamics Culture dynamics Social dynamics Language dynamics Crowed behaviors

4 Social Knowledge Dynamics “Knowledge is embodied in people gathered in communities and networks. The road to knowledge is via people, conversations, connections and relationships. Knowledge surfaces through dialog, all knowledge is socially mediated and access to knowledge is by connecting to people that know or know who to contact.” -- Denham Grey Social dynamics: ➢ A society of individuals to react to inner and/or outer changes; ➢ Global patterns can emerge from even simple individuals; ➢ phase transitions, catastrophe, etc. Social Dynamics Social knowledge dynamics Culture dynamics Language dynamics Crowed behaviors … …

Difficulties and motivations Two levels of difficulty to discover global emergence by local dynamic models: The definition of sensible and realistic microscopic models (intact data is needed) The usual problem of inferring the macroscopic phenomena out of the microscopic dynamic models i Motivations of studying Wikipedia The formation of Wikipedia is a kind of social knowledge dynamics; (if treat articles as knowledge Intact data for download Articles, categories, images and multimedia, talk pages, redirect and broken links and so on

5 Difficulties and Motivations ❖ Two levels of difficulty to discover global emergence by local dynamic models: ➢ The definition of sensible and realistic microscopic models; (intact data is needed) ➢ The usual problem of inferring the macroscopic phenomena out of the microscopic dynamic models; ❖ Motivations of studying Wikipedia – The formation of Wikipedia is a kind of social knowledge dynamics; (if treat articles as knowledge) – Intact data for download; • Articles, categories, images and multimedia, talk pages, redirect and broken links, and so on

Related Analysis on Wikipedia B treat Wikipedia as complex networks where the articles represent the nodes, and hyperlinks represent links Degree distribution Reciprocity and feedback loops Motifs

6 Related Analysis on Wikipedia ❖ Treat Wikipedia as complex networks, where the articles represent the nodes, and hyperlinks represent links. Degree distribution Reciprocity and feedback loops Motifs

Degree distribution o Degree: measure the number of articles that link into or out of eanings of degree Two articles sharing a link reflect some kind of relations in term of their contents Articles with high degree are more likely to be common knowledge

7 Degree distribution • Degree: measure the number of articles that link into or out of • Meanings of degree: – Two articles sharing a link reflect some kind of relations in term of their contents; – Articles with high degree are more likely to be common knowledge;

Observations: Scale-free 10 10 The in-degree distribution of Japan The out-degree distribution of Wikipedia.(adopted from Fig. 3 in Japan Wikipedia.(adopted from f11) Fig 3 in ref[ 1].) Reference [1V. Zlatic, M. Bozicevic, H Stefancic, and M. Domazet, Wikipedias: Collaborative Web-based Encyclopedias as Complex Networks", Physical Review E 74, 016615, 2006.8

8 Observations: Scale-free The in-degree distribution of Japan Wikipedia. (adopted from Fig. 3 in ref[1].) Reference [1] V. Zlatic, M. Bozicevic, H. Stefancic, and M. Domazet, “Wikipedias: Collaborative Web-based Encyclopedias as Complex Networks”, Physical Review E 74, 016615, 2006. The out-degree distribution of Japan Wikipedia. (adopted from Fig. 3 in ref[1].)

Scale-free and phase Transition that the road from disorder to order is maintained or The theory of phase transitions told us loud and cle the powerful forces of self-organization and is paved by power laws. It told us that power laws are the patent signatures of self-organization in complex systems Barabasi aL. 2002. Linked The new science of networks. Cambridge Perseus Publishing Similar results can be observed from Wikipedia with other languages What are the fundamental principle behind the similar type of growth? -Preferential Attachment?

9 Scale-free and Phase Transition “The theory of phase transitions told us loud and clear that the road from disorder to order is maintained by the powerful forces of self-organization and is paved by power laws. It told us that power laws are the patent signatures of self-organization in complex systems….” --Barabasi AL. 2002. Linked: The new science of networks. Cambridge: Perseus Publishing. Similar results can be observed from Wikipedia with other languages. What are the fundamental principle behind the similar type of growth? – Preferential Attachment?

Reciprocity and Feedback Loops Reciprocal links are just the links pointing from the node i to the node j for which exists a link pointing from node i to the node i bd L a=L/N(N-1) The density of the links Reciprocity qualifies mutual" exchange"between two articles Feedback loops: A loop with directed links that start from and end with the same node 10

10 Reciprocity and Feedback Loops • Reciprocal links are just the links pointing from the node i to the node j for which exists a link pointing from node j to the node i. Reciprocity qualifies mutual “exchange” between two articles. • Feedback loops: A loop with directed links that start from and end with the same node. a L N N = − / ( 1) The density of the links