1 measurement and analysis of online social networks a. mislove, m. marcon, k gummadi, p. druschel,...
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Measurement and Analysis of Online Social Networks
A. Mislove, M. Marcon, K Gummadi, P. Druschel, B. Bhattacharjee
Presentation byYong Wang
(Defense side)
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My general opinion
• This is a brilliant paper.
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Title
• Let’s recall the title of this course.
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“There are no
accidents”
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Author• Who is this guy?
Alan Mislove
At least six papers on OSN published within two years to top-class conferences, like WWW, IMC, WOSN, NSDI..
We will read two of them in the next two months
This paper- 16 citations already in one year
From Rice Univ. Social relationship
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Contributions• Introduce what online social networks are
definition section 2
• Measure online social networks at scale
data section 4
• Introduce static structural properties
results section 5
• Explain why study online social networks?
impact section 5 + section 6
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What are (online) social networks?
• Social networks are graphs of people
Graph edges connect friends
• Online social networking Social network hosted by a Web site
Friendship represents shared interest or trust
Online friends may have never met
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Data -- Measure online social networks at scale
• This paper presents a large-scale measurement study and analysis on four online social networks containing over 11.3 million users and 328 million links.
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Site YT Flickr LJ Orkut
Users(mill)
1.1 1.8 5.2 3
Links(mill)
4.9 22 72 223
Traffic ranking in Alexa
3 34 88 102
Coverage Rich media --video
Rich media – photo
Blog “Pure”OSN
Data are representative
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How large the scale is?
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Paper Site proportion
This paper Orkut 11.3%
Analysis of Topological Characteristics of Huge Online
Social Networking Services (WWW’07)
Orkut 0.3%
This paper LiveJournal 95.4%Group Formation in Large Social
Networks: Membership, Growth, and Evolution (KDD’06)
LiveJournal 0.08%
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Why study the graphs?• important to improve existing system and
develop new applications
– information search
• Web search: PeerSpective [HotNets’06]
– trusted users
• Trust can be used to solve security problems
• Multiple identity attacks: SybilGuard [SIGCOMM’06]
• Spam: RE [NSDI’06]
• Ostra: thwart unwanted communication [NSDI’08]
• Understanding network structure is necessary first step
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Information searchLocating content
• Comparison between Google and OSN
• How Google comes and works?
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Search on OSN • The integration of search engines and
online social networks could enable queries such as
• "Has any of my acquaintances been on holidays in New Zealand?" or
• "Recent articles on hypertext authored by people associated with Ted Nelson".
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Results+Impacts
• Link symmetry
• Power-law node degrees
• Correlation of indegree and outdegree
• Path lengths and diameter
• Link degree correlations
• Densely connected core
• Tightly clustered fringe
• Groups
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Link symmetry
• Social networks show high level of link symmetry
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In the WEB (CNN- “a dancing queen” in the web) Things are different in OSN due to reciprocation
In the OSN world, “the dancing queen” may place a link pointing back to other “gentlemen”, although not 100%..
likelihood is much higher
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Implications of high symmetry
Implications is that ‘hubs’ become ‘authorities’
May impact search algorithms (PageRank, HITS)
Open a research direction for others, e.g.
“The Karma of Digg: Reciprocity in Online Social Networks” by E. Sadlon et al. in 2008
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Power-law node degrees
16U.S. highways U.S. Airlines
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Power-law node degrees• In the WEB (CNN vs. personal webpages)
• In the OSN- power-law. as well, after all, it is second life
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• In the WEB, the indegree and outdegree power-law exponents differ significantly• In the OSNs, the power-law exponents for the indegree and outdegree distributions in each of the social networks are very similar
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Power-law node degrees• The differences show that : In the WEB, the
incoming links are significantly more concentrated on a few high-degree nodes than the outgoing links
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In all social networks, distributions of incoming and outgoing links across the nodes are very similar.
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Implications of Power-law degrees
• Realize the structure of OSN --- power-law.
• nodes with many incoming links (hubs) have value due to their connection to many users
• it becomes easy to spread important information to the other nodes, e.g. DNS
• in order for a user to send spam, they have to become a more important node, amass friends. introduced at • “SybilGuard : [SIGCOMM’06]” and
• “Ostra : [NSDI’08]”
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Correlation of indegree and outdegree
• In WEB, most nodes have considerably higher outdegree than indegree, while a small fraction of nodes have significantly higher indegree than outdegree. (CNN vs. personal webpages)
• In social networks, the nodes with very high outdegree also tend to have very high indegree
• The famous people who know lots of people also is known by lost of people
PW CNN
OSN
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Implications of Correlation of indegree and outdegre
• The high correlation between indegree and outdegree in social networks can be explained by the high number of symmetric links
• The high symmetry may be due to the tendency of users to reciprocate links from other users who point to them.
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Search information : makes it harder to identify reputable sources due to dilutionpossible sol: who initiated the link?
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Path lengths and diameter• all four networks have short path length
from 4.25 – 5.88
• six degrees of separation
Facebook, 4.2 million for Octorber 2007, 6.12 fromhttp://blog.paulwalk.net/2007/10/08/no-degrees-of-separation/
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Implications of Path lengths and diameter
The small diameter and path lengths of social networks are likely to impact the design of techniques for finding paths in such networks
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Link degree correlations• high-degree nodes tend to connect to other high-degree nodes ? OR
• high-degree nodes tend to connect to low-degree nodes ?
• In real society: the former theory is true.
• By virtue of two metrics: the scale-free metric and the assortativity.
• Suggests that there exists a tightly-connected “core” of the high-degree nodes which connect to each other, with the lower-degree nodes on the fringes of the network.
• The next question: How big the core is
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Implications of Link degree correlationsSpread of Information
“A Measurement-driven Analysis of Information Propagation in the Flickr Social Network” [WWW’ 09]
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Densely connected core
• the graphs have a densely connected core comprising of between 1% and 10% of the highest degree nodes such that removing this core completely disconnects the graph.
Sub logarithmic growth
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Implications of densely connected core
• Network contains dense core of users
Core necessary for connectivity of 90% of users
Most short paths pass through core
Could be used for quickly disseminating information
• So 10% at core
• What about remaining nodes (90% at fringe)
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Tightly clustered fringe• Clustering Coefficient of a network:
How many of your friends are also friends themselves?
• social network graphs show stronger clustering, most likely because: people tend to be introduced to other people via mutual friends, increasing the probability that two friends of a single user are also friends.
Are the fringes more clustered?
The clustering coefficient is higher for nodes of low degree
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Implications of Tightly clustered fringe
• Fringe is highly clusteredUsers with few friends form mini-cliques
Similar to previously observed offline behavior
Could be leveraged for sharing information of local interest
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Groups• group sizes follow power-law distribution
• the members of smaller user groups tend to be more clustered than those of larger groups
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Groups
• Low-degree nodes tend to be part of very few communities, while high-degree nodes tend to be members of multiple groups.
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Implications of Groups
• “To Join or Not to Join: The Illusion of Privacy in Social Networks with Mixed Public and Private User Profiles” [WWW’ 09]
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• Finally, Give details and reasons for all deviations , that is good
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What does the structure look like
the networks contain a densely connected core of high-degree nodes;
and that this core links small groups of strongly clustered, low-degree nodes at the fringes of the network.octopus
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Two stories
• This paper shows its brilliance in the same way
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