Difference between revisions of "Liben-Nowell Kleinberg J. Am.Soc.Inf.Sci.2007"

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The Link-Prediction Problem for Social Networks
 
The Link-Prediction Problem for Social Networks
 
This is not a final version, under construction!
 
  
 
== Citation ==
 
== Citation ==
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Given a social network <math>G = <V, E></math> in which each edge represents an interaction at a particular time <math>t(e)</math>. For two times <math>t < t^'</math>, <math>G[t, t^']</math> denote the sub-graph of <math>G</math> consisting of all edges representing the interactions happening between <math>t</math> and <math>t^'</math>. A link-prediction problem can be formalized as given four time <math>t_0 < t^'_0 < t_1 < t^'_1</math> and the network <math>G[t_0, t^'_0]</math>, to output or predict a list of edges not present in <math>G[t_0, t^'_0]</math> but appear in the network <math>G[t_1, t^'_1]</math>.
 
Given a social network <math>G = <V, E></math> in which each edge represents an interaction at a particular time <math>t(e)</math>. For two times <math>t < t^'</math>, <math>G[t, t^']</math> denote the sub-graph of <math>G</math> consisting of all edges representing the interactions happening between <math>t</math> and <math>t^'</math>. A link-prediction problem can be formalized as given four time <math>t_0 < t^'_0 < t_1 < t^'_1</math> and the network <math>G[t_0, t^'_0]</math>, to output or predict a list of edges not present in <math>G[t_0, t^'_0]</math> but appear in the network <math>G[t_1, t^'_1]</math>.
  
== Brief description of the method ==
+
== A List of Methods for Link Prediction ==
The algorithm takes a written review as an input. First it assigns a POS tag to each word in the review to identify adjective or adverb phrases in the input review. They have used PMI-IR algorithm to estimate the semantic orientation of a phrase. The Pointwise Mutual Information (PMI) between two words <math> w_1 </math> and <math> w_2 </math> is defined as follow:
+
All the following methods assign a connection weight <math>\textrm{score}(x,y)</math> to node pair <math><x,y></math>. We can group them in a less strict way and you can check the definition of each method in its own page.
  
<math>
+
{| class="wikitable" border="1"
PMI(w_1,w_2)=log_2(p(w_1\ and\ w_2)/p(w_1)p(w_2))
+
|-
</math>
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| Methods Based on Node Neighborhoods || [[Methods::Common neighbors]], [[Methods::Jaccard's Coefficient]], [[Methods::Adamic/Adar]], [[Methods::Preferential Attachment]]
 +
|-
 +
| Methods Based on the Ensemble of All Paths || [[Methods::Katz]], [[Methods::Hitting time]]
 +
|-
 +
| Others || graph distance, [[Methods::SimRank]]
 +
|}
  
where <math> p(w_1,w_2) </math> is the probability that <math> w_1 </math> and <math> w_2 </math> co-occur. They have defined the semantic orientation of a phrase as follow:
+
== Data sets and Experiments ==
 +
The paper works with five co-authorship networks, obtained from the author lists of articles contained in five sections of the physics e-Print arXiv. The training interval is defined to be the 3 years from 1994 through 1996 and test interval to be the 3 years from 1997 through 1999.
  
<math>
+
Each link predictor outputs a ranked list of pairs and the paper takes the first <math>n</math>, which is the number of new links from the test set, and count how many of edges from these <math>n</math> are in the test set.
SO(phrase)=PMI(phrase,'excellent')-PMI(phrase,'poor')
 
</math>
 
  
We can modify the above definition to obtain the following formula:
+
== Result ==
 +
The performance is compared with a random predictor.
  
<math>
+
[[File:LN_K_2007_Result.jpg]]
SO(phrase)=log_2(\frac{hits(phrase\ NEAR\ 'excellent')hits('excellent')}{hits(phrase\ NEAR\ 'poor')hits('poor')} )
 
</math>
 
  
where operator NEAR means that the two phrases should be appeared close to each other in the corpus. Using the above formula they have calculated the average semantic orientation for a review. They have shown that the value of average semantic orientation for phrases in the items that are tagged as "recommended" by the users are usually positive and those that are tagged as "not recommended" are usually negative.
+
We can see that Adamic/Adar outperforms other methods and for more detailed results please refer to the paper.
  
== Experimental Result ==
+
== Related papers ==
 
+
Most link prediction solutions can fall to two directories, one is to use topological features and the other is to use node or edge information.
This approach was fairly successful on a range of review-classification tasks: it achieved accuracy of between 65% and 85% in predicting an author-assigned "recommended" flag for Epinions ratings for eight diverse products, ranging from cars to movies. Many later writers used several key ideas from the paper, including: treating polarity prediction as a document-classification problem; classifying documents based on likely-to-be-informative phrases; and using unsupervised or semi-supervised learning methods.
 
  
== Related papers ==
+
[[RelatedPaper::Link propagation: A fast semi-supervised learning algorithm for link prediction]] suggests a semi-supervised framework which need a node similarity matrix as input. Many applications like protein-protein interactions and social networks are able to provide this information.
  
The widely cited [[RelatedPaper::Pang et al EMNLP 2002]] paper was influenced by this paper - but considers supervised learning techniques.  The choice of movie reviews as the domain was suggested by the (relatively) poor performance of Turney's method on movies.
+
[[RelatedPaper::Supervised Random Walks: Predicting and Recommending Links in Social Networks]] adopts a random walk framework and use edge and node information as features to train a transition rate over each edge to maximize the probability of random walk stopping time on positive nodes.
  
An interesting follow-up paper is [[RelatedPaper::Turney and Littman, TOIS 2003]] which focuses on evaluation of the technique of using PMI for predicting the [[semantic orientation of words]].
+
== Study Plan ==
 +
* About Adamic/Adar score
 +
**[[Paper::Adamic, L.A., & Adar, E. (2003). Friends and neighbors on the Web. Social Networks, 25(3), 211–230]]
 +
* To understand which graph information these features represent
 +
**[[Paper::Davidsen, J., Ebel, H., & Bornholdt, S. (2002). Emergence of a small world from local interactions: Modeling acquaintance networks. Physical Review Letters, 88(128701)]]

Latest revision as of 02:10, 27 September 2012

The Link-Prediction Problem for Social Networks

Citation

Liben-Nowell, D. and Kleinberg, J. (2007), The link-prediction problem for social networks. J. Am. Soc. Inf. Sci., 58: 1019–1031. doi: 10.1002/asi.20591

Online version

PDF

Summary

This paper extensively evaluates many unsupervised methods using topological features of the network for link prediction and compares their performances over different data sets. The result shows that Adamic-Adar, which measures the node similarity, has the best performance.

Problem Setup

Given a social network in which each edge represents an interaction at a particular time . For two times , denote the sub-graph of consisting of all edges representing the interactions happening between and . A link-prediction problem can be formalized as given four time and the network , to output or predict a list of edges not present in but appear in the network .

A List of Methods for Link Prediction

All the following methods assign a connection weight to node pair . We can group them in a less strict way and you can check the definition of each method in its own page.

Methods Based on Node Neighborhoods Common neighbors, Jaccard's Coefficient, Adamic/Adar, Preferential Attachment
Methods Based on the Ensemble of All Paths Katz, Hitting time
Others graph distance, SimRank

Data sets and Experiments

The paper works with five co-authorship networks, obtained from the author lists of articles contained in five sections of the physics e-Print arXiv. The training interval is defined to be the 3 years from 1994 through 1996 and test interval to be the 3 years from 1997 through 1999.

Each link predictor outputs a ranked list of pairs and the paper takes the first , which is the number of new links from the test set, and count how many of edges from these are in the test set.

Result

The performance is compared with a random predictor.

LN K 2007 Result.jpg

We can see that Adamic/Adar outperforms other methods and for more detailed results please refer to the paper.

Related papers

Most link prediction solutions can fall to two directories, one is to use topological features and the other is to use node or edge information.

Link propagation: A fast semi-supervised learning algorithm for link prediction suggests a semi-supervised framework which need a node similarity matrix as input. Many applications like protein-protein interactions and social networks are able to provide this information.

Supervised Random Walks: Predicting and Recommending Links in Social Networks adopts a random walk framework and use edge and node information as features to train a transition rate over each edge to maximize the probability of random walk stopping time on positive nodes.

Study Plan