Young Scientist Semiotic dynamics in online social communities

A distributed classification paradigm known as collaborative tagging has been successfully deployed in large-scale web applications designed to manage and share diverse online resources. Users of these applications organize resources by associating with them freely chosen text labels, or tags. Here we regard tags as basic dynamical entities and study the semiotic dynamics underlying collaborative tagging. We collect data from a popular system and focus on tags associated with a given resource. We find that the frequencies of tags obey to a generalized Zipf’s law and show that a Yule–Simon process with memory can be used to explain the observed frequency distributions in terms of a simple model of user behavior 1 Collaborative Tagging A new paradigm has been quickly gaining ground in information systems on the World Wide Web: collaborative tagging [1, 2]. In web-based applications like Del.icio.us, Flickr, CiteULike, users enrich diverse resources – ranging from photographs to scientific references and web pages – with semantically meaningful information in the form of text labels, or “tags”. Tags are freely chosen and users associate resources with them in a totally uncoordinated fashion, for their own use. The tagging activity of each user is globally visible to the user community (see Fig. 1) and the tagging process develops genuine social aspects and complex interactions. Remarkably, despite the selfish nature of users’ behavior, tagging systems exhibit cooperative dynamics that eventually lead to a bottom-up categorization of resources, shared throughout the user community. The open-ended set of tags used within the system – commonly referred to as “folksonomy” – can be used as a sort of semantic map to navigate the contents of the system itself. It has been argued that the surging popularity of collaborative tagging is due to its comparatively small cognitive overhead with respect to taxonomic categorization [1, 3], so that tagging is a very natural activity for web users. Collaborative tagging systems leverage this aspect, recruiting simple and robust a e-mail: ciro.cattuto@roma1.infn. it 1 http://del.icio.us/ 2 http://flickr.com/ 3 http://citeulike.org/ behaviors of individual users in order to create cooperation and foster the emergence of shared conventions at the system level. Focusing on tags as basic dynamical entities, collaborative tagging falls within the scope of semiotic dynamics [4, 5], a new field that studies how populations of humans or agents can establish and share semiotic systems, typically driven by their use in communication. New web applications hinged on collaborative tagging fall precisely in this perspective and can be regarded as cases of semiotic dynamics at play: folksonomies, in fact, do exhibit dynamical aspects also observed in human languages [6, 7], such as the emergence of naming conventions, competition between terms, takeovers by neologisms, and more. In the following we briefly describe the structure of collaborative tagging systems and discuss the experimental procedures that we employ to collect data from Del. icio.us, one of the most popular and paradigmatic social bookmarking systems. We adopt a resource-centric view of the system and focus on the tags that have been associated with a given resource. We report on the distribution of tag frequencies and show that a stochastic Yule–Simon process with memory can be used to successfully describe the observed frequency distributions. We close by casting our work in a more general research perspective.