A 13th century social network

According to Nature News, a team of French researchers has used medieval documents to create the oldest detailed social network ever constructed. The mathematicians and computer scientists looked through thousands of records of land transactions dating back as far as 1260 in a Southwest part of France. The result of their study shows 'how medieval peasants and lords were connected.' Even if the title of the Nature News article is somewhat ironic -- 'Researchers give a French province the 'Facebook' treatment' --, this mathematical study is pretty serious. And its title is more enigmatic: 'Batch kernel SOM and related Laplacian methods for social network analysis' (SOM meaning 'self-organizing map'). But read more...

According to Nature News, a team of French researchers has used medieval documents to create the oldest detailed social network ever constructed. The mathematicians and computer scientists looked through thousands of records of land transactions dating back as far as 1260 in a Southwest part of France. The result of their study shows 'how medieval peasants and lords were connected.' Even if the title of the Nature News article is somewhat ironic -- 'Researchers give a French province the 'Facebook' treatment' --, this mathematical study is pretty serious. And its title is more enigmatic: 'Batch kernel SOM and related Laplacian methods for social network analysis' (SOM meaning 'self-organizing map'). But read more...

A French medieval social network

You can see above "a representation of the medieval social network with force directed algorithm." (Credit: Romain Boulet et al.) This figure has been made by using the open source graph drawing Tulip software.

This research work has been done by Romain Boulet, Bertrand Jouve and Nathalie Villa of the Institut de mathématiques de Toulouse. Fabrice Rossi, a researcher at the The French National Institute for Research in Computer Science and Control (INRIA), was the fourth member of the team. [Note: some of the links in this paragraph lead to pages written in French.]

[(Update: May 23, 2008) Bertrand Jouve, one of the authors of this research work, sent me today a message about the illustration shown above which I apparently wrongly attributed to "Romain Boulet et al." Jouve writes: "The study of that network with force-based algorithm is due to Pascale Kuntz, Fabien Picarougne and Bleuenn Legoffic, partners of the project. They are from the LINA (CNRS, Nantes University, France)." In the preprint version of the paper I've seen, I must say there were no references to these scientists. The researchers listed by Jouve were only mentioned at the end of the preprint paper, in the "Acknowledgments" section: "We also want to thank Fabien Picarougne and Bleuenn Le Goffic (LINA, Polytech’Nantes, France) for managing the database registration and Pascale Kuntz for her expertise in graph vizualization." How could I've guessed they were the authors of the above diagram if the lead researchers don't even mention it in their article?]

You all know that the French Revolution happened at the end of the 18th century. Many official documents were destroyed during this troubled period. As said Villa, "documents showing medieval landholdings have been preserved in other parts of Europe, but are relatively rare in France. In France, most of these types of documents disappeared during the revolution. There is little documentation of how peasants lived their lives." But in Lot, records of thousands of land transactions survived intact. Villa and her colleagues examined roughly 1,000 contracts, deeds and other documents stored in an online database, and analysed the social ties between the people featured in them.

As Nature News says, some results of this study were very predictable. But other ones were unexpected. "For example, some well-connected peasants had a surprising number of social links beyond their village. And analysis of later documents also shows that the network may have changed substantially over the course of the Hundred Years' War -- a prolonged conflict that smouldered on and off from 1337 to 1453, as two prominent families vied for the French throne."

For more information, this research work has been published in Neurocomputing, an Elsevier scientific journal. This article was part of a special issue named "Progress in Modeling, Theory, and Application of Computational Intelligence - 15th European Symposium on Artificial Neural Networks 2007" (Volume 71, Issues 7-9, Pages 1117-1768, March 2008).

Here is a link to the abstract of "Batch kernel SOM and related Laplacian methods for social network analysis" (Pages 1257-1273). "Large graphs are natural mathematical models for describing the structure of the data in a wide variety of fields, such as web mining, social networks, information retrieval, biological networks, etc. For all these applications, automatic tools are required to get a synthetic view of the graph and to reach a good understanding of the underlying problem. In particular, discovering groups of tightly connected vertices and understanding the relations between those groups is very important in practice. This paper shows how a kernel version of the batch self-organizing map can be used to achieve these goals via kernels derived from the Laplacian matrix of the graph, especially when it is used in conjunction with more classical methods based on the spectral analysis of the graph. The proposed method is used to explore the structure of a medieval social network modelled through a weighted graph that has been directly built from a large corpus of agrarian contracts."

And here is another link to a preprint version of the paper (PDF format, 17 pages, 1.79 MB), from which the above illustration has been extracted.

Sources: Geoff Brumfiel, Nature News, May 19, 2008; and various websites

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