Leskovec, J. & Horvitz, E.: Planetary-scale views on a large instant-messaging network. WWW '08: Proceeding of the 17th international conference on World Wide Web. New York, NY, USA: ACM, 2008, S. 915-924
[Volltext]
We present a study of anonymized data capturing a month of high-level communication activities within the whole of the Microsoft Messenger instant-messaging system. We examine characteristics and patterns that emerge from the collective dynamics of large numbers of people, rather than the actions and characteristics of individuals. The dataset contains summary properties of 30 billion conversations among 240 million people. From the data, we construct a communication graph with 180 million nodes and 1.3 billion undirected edges, creating the largest social network constructed and analyzed to date. We report on multiple aspects of the dataset and synthesized graph. We find that the graph is well-connected and robust to node removal. We investigate on a planetary-scale the oft-cited report that people are separated by "six degrees of separation" and find that the average path length among Messenger users is 6.6. We find that people tend to communicate more with each other when they have similar age, language, and location, and that cross-gender conversations are both more frequent and of longer duration than conversations with the same gender.

Crestani, F.: Application of Spreading Activation Techniques in Information Retrieval. In: Artificial Intelligence Review 11 (1997), Nr. 6, S. 453-482
[Volltext]
This paper surveys the use of Spreading Activation techniques onSemantic Networks in Associative Information Retrieval. The majorSpreading Activation models are presented and their applications toIR is surveyed. A number of works in this area are criticallyanalyzed in order to study the relevance of Spreading Activation forassociative IR.
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Salton, G. & Buckley, C.: On the use of spreading activation methods in automatic information. SIGIR '88: Proceedings of the 11th annual international ACM SIGIR conference on Research and development in information retrieval. New York, NY, USA: ACM Press, 1988, S. 147-160
[Volltext]
Spreading activation methods have been recommended in information retrieval to expand the search vocabulary and to complement the retrieved document sets. The spreading activation strategy is reminiscent of earlier associative indexing and retrieval systems. Some spreading activation procedures are briefly described, and evaluation output is given, reflecting the effectiveness of one of the proposed procedures.